Patent Publication Number: US-2023143293-A1

Title: Biometric authentication using a smart ring

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/877,391, filed Jul. 23, 2019, and U.S. Provisional Patent Application No. 62/980,722, filed Feb. 24, 2020, both incorporated by reference herein for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to implementations of smart ring wearable devices and, more particularly, to authentication techniques using smart ring wearable devices. 
     BACKGROUND 
     To obtain authorization to access digital and physical resources, a person generally must provide a security system with an identity. The security system also typically needs some form of authentication from the person in order to ensure that the person actually matches their professed identity. Three common forms of authentication include: something the person knows (e.g., a password), something the person has (e.g., a key, card, or token generator), or something the person is (e.g., biometrics such as a fingerprint). These forms of authentication can be combined to enable multi-factor authentication. 
     Conventional security devices used to facilitate authentication, such as keys, cards, and smartphones, can easily be stolen or misplaced. On the other hand, more permanent solutions such as chip implants and tattoos are invasive and hard to upgrade and/or replace. Further, often these devices only support one form of authentication and their capabilities are not flexible enough to accommodate different combinations of multi-factor authentication. 
     As one example, hardware wallets have been introduced to store and generate keys used to authenticate a person wishing to complete cryptographic operations. These hardware wallets are generally in the form of a Universal Serial Bus (USB) device or smart card. These conventional devices are easy to lose or misplace. Furthermore, these conventional devices cannot take advantage of many forms of authentication, such as certain biometric signatures and gesture patterns that a device such as a smart card would not be able to measure. 
     BRIEF SUMMARY 
     The authentication techniques and devices described below address many problems with conventional security devices and techniques. The described authentication techniques utilize a smart ring as an authentication device that is portable, easy to keep on the person, and able to support a wider variety of authentication forms. The smart ring can easily and inconspicuously be worn by a person wherever they go. Moreover, the smart ring can support many individual authentication forms and combinations of authentication forms that conventional security devices cannot. Because the smart ring is worn on a person&#39;s hand, the smart ring can capture a variety of biometric data, subtle gestures, and proximity effects with other devices such as other rings. The person can move and perform gestures freely, without needing to carry a separate authentication device. 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. Certain embodiments may include features and advantages not described in this summary. Further, certain embodiments may omit one or more (or all) of the features and advantages described in this summary. 
     One example embodiment is a method performed by a smart ring including collecting, by one or more sensors of the smart ring, biometric data of a particular user while the particular user is wearing the smart ring. The biometric data may include a heartbeat pattern of the particular user. The method further includes performing an authentication operation by: (i) comparing the biometric data to a biometric signature for a known user to determine whether the biometric data matches the biometric signature and (ii) when the biometric data matches the biometric signature, authenticating the particular user by updating a record to indicate that the particular user has been identified and authenticated as the known user. Moreover, the method includes, when the record indicates that the particular user has been identified and authenticated, responding to said authenticating by digitally signing transaction data using a private cryptographic key stored on a memory of the smart ring. 
     An additional embodiment is a smart ring comprising a housing configured to be worn by a user on a finger of the user, one or more sensors, a memory, and a processor. The one or more sensors may be configured to collect biometric data of a particular user while the particular user is wearing the smart ring. The biometric data may include a heartbeat pattern of the particular user. Further, the processor may be configured to perform an authentication operation by: (i) comparing the biometric data to a biometric signature for a known user to determine whether the biometric data matches the biometric signature, and (ii) when the biometric data matches the biometric signature, authenticating the particular user by updating a record to indicate that the particular user has been identified and authenticated as the known user. The processor may also be configured to, when the record indicates that the particular user has been identified and authenticated, respond to said authenticating by digitally signing transaction data using a private cryptographic key stored on the memory of the smart ring. 
     Depending upon the embodiment, one or more benefits may be achieved. These benefits and various additional objects, features and advantages of the present disclosure can be fully appreciated with reference to the detailed description and accompanying drawings that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Each of the figures described below depicts one or more aspects of the disclosed system(s) and/or method(s), according to an embodiment. Wherever possible, the detailed description refers to the reference numerals included in the following figures. 
         FIG.  1    illustrates a system comprising a smart ring and a block diagram of smart ring components according to some embodiments. 
         FIG.  2    illustrates a number of different form factor types of a smart ring according to some embodiments. 
         FIG.  3    illustrates examples of different smart ring form factors. 
         FIG.  4    illustrates an environment within which a smart ring may operate according to some embodiments. 
         FIG.  5    illustrates an example method for identifying and authenticating a user using biometric data collected by a smart ring according to one embodiment. 
         FIG.  6 A  and  FIG.  6 B  illustrate an example method for performing multi-factor authentication using a smart ring according to one embodiment. 
         FIG.  7    illustrates an example method for identifying and authenticating a user using contact data collected by a smart ring indicating a sequence of taps of the smart ring according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates a system  100  comprising (i) a smart ring  101  including a set of components  102  and (ii) one or more devices or systems that may be electrically, mechanically, or communicatively connected to the smart ring  101 . Specifically, the system  100  may comprise any one or more of: a charger  103  for the smart ring  101 , a user device  104 , a network  105 , a mobile device  106 , or a server  107 . The charger  103  may provide energy to the smart ring  101  by way of a direct electrical, a wireless, or an optical connection. The smart ring  101  may be in a direct communicative connection with the user device  104 , the mobile device  106 , or the server  107  by way of the network  105 . Interactions between the smart ring  101  and other components of the system  100  are discussed in more detail in the context of  FIG.  4   . 
     The smart ring  101  may sense a variety of signals indicative of activities of a user wearing the ring  101 , biometric signals, a physiological state of the user, or signals indicative of the user&#39;s environment. The smart ring  101  may analyze the sensed signals using built-in computing capabilities or in cooperation with other computing devices (e.g., user device  104 , mobile device  106 , server  107 ) and provide feedback to the user or about the user via the smart ring  101  or other devices (e.g., user device  104 , mobile device  106 , server  107 ). By analyzing the sensed signals (e.g., representing sensed biometric information such as a heart rate signature or pattern, sensed motion information corresponding to gestures, and sensed proximity or contact information), the smart ring  101  (possibly in cooperation with other computing devices) may identify and authenticate a wearer of the smart ring  101  as a particular known user. In response to authenticating a wearer as a known user, the smart ring  101  may grant access to resources and/or perform certain operations, including cryptographic operations, to be discussed more in detail in the context of  FIG.  5   ,  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   . Additionally or alternatively, the smart ring  101  may provide the user with notifications sent by other devices, enable secure access to locations or information, or a variety of other applications pertaining to health, wellness, productivity, or entertainment. 
     The server  107  may include one processor  108  and at least one non-transitory computer-readable memory  109  storing instructions executable on the processor  108 . The server  107  may be an authentication server that supports the smart ring  101 &#39;s authentication functionalities. For example, the server  107  can store data pertaining to identified users (e.g., wearers) of the smart ring  101 . The server  107  may perform data analysis to identify and authenticate users of the smart ring  101  and/or perform operations relating to authentication, as described in further detail with respect to  FIG.  5   ,  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   . While not depicted as such in  FIG.  1   , it is understood that the server  107  may be one of several servers. Further, the server  107  may be implemented as part of a cloud computing service, or may be a node of a decentralized blockchain. 
     The smart ring  101 , which may be referred to herein as the ring  101 , may comprise a variety of mechanical, electrical, optical, or any other suitable subsystems, devices, components, or parts disposed within, at, throughout, or in mechanical connection to a housing  110  (which may be ring shaped and generally configured to be worn on a finger). Additionally, a set of interface components  112   a  and  112   b  may be disposed at the housing, and, in particular, through the surface of the housing. The interface components  112   a  and  112   b  may provide a physical access (e.g., electrical, fluidic, mechanical, or optical) to the components disposed within the housing. The interface components  112   a  and  112   b  may exemplify surface elements disposed at the housing. As discussed below, some of the surface elements of the housing may also be parts of the smart ring components. 
     As shown in  FIG.  1   , the components  102  of the smart ring  101  may be distributed within, throughout, or on the housing  110 . As discussed in the contexts of  FIG.  2    and  FIG.  3    below, the housing  110  may be configured in a variety of ways and include multiple parts. The smart ring components  102  may, for example, be distributed among the different parts of the housing  110 , as described below, and may include surface elements of the housing  110 . The housing  110  may include mechanical, electrical, optical, or any other suitable subsystems, devices, components, or parts disposed within or in mechanical connection to the housing  110 , including a battery  120 , a charging unit  130 , a controller  140 , a sensor unit  150  comprising one or more sensors, a communications unit  160 , a one or more user input devices  170 , or a one or more output devices  190 . Each of the components  120 ,  130 ,  140 ,  150 ,  160 ,  170 , and/or  190  may include one or more associated circuits, as well as packaging elements. The components  120 ,  130 ,  140 ,  150 ,  160 ,  170 , and/or  190  may be electrically or communicatively connected with each other (e.g., via one or more busses or links, power lines, etc.), and may cooperate to enable “smart” functionality described within this disclosure. 
     The battery  120  may supply energy or power to the controller  140 , the sensors  150 , the communications unit  160 , the user input devices  170 , or the output devices  190 . In some scenarios or implementations, the battery  120  may supply energy or power to the charging unit  130 . The charging unit  130 , may supply energy or power to the battery  120 . In some implementations, the charging unit  130  may supply (e.g., from the charger  103 , or harvested from other sources) energy or power to the controller  140 , the sensors  150 , the communications unit  160 , the user input devices  170 , or the output devices  190 . In a charging mode of operation of the smart ring  101 , the average power supplied by the charging unit  130  to the battery  120  may exceed the average power supplied by the battery  120  to the charging unit  130 , resulting in a net transfer of energy from the charging unit  130  to the battery  120 . In a non-charging mode of operation, the charging unit  130  may, on average, draw energy from the battery  120 . 
     The battery  120  may include one or more cells that convert chemical, thermal, nuclear or another suitable form of energy into electrical energy to power other components or subsystems  140 ,  150 ,  160 ,  170 , and/or  190  of the smart ring  101 . The battery  120  may include one or more alkaline, lithium, lithium-ion and or other suitable cells. The battery  120  may include two terminals that, in operation, maintain a substantially fixed voltage of 1.5, 3, 4.5, 6, 9, 12 V or any other suitable terminal voltage between them. When fully charged, the battery  120  may be capable of delivering to power-sinking components an amount of charge, referred to herein as “full charge,” without recharging. The full charge of the battery may be 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 10000, 20000 mAh or any other suitable charge that can be delivered to one or more power-consuming loads as electrical current. 
     The battery  120  may include a charge-storage device, such as, for example a capacitor or a super-capacitor. In some implementations discussed below, the battery  120  may be entirely composed of one or more capacitive or charge-storage elements. The charge storage device may be capable of delivering higher currents than the energy-conversion cells included in the battery  120 . Furthermore, the charge storage device may maintain voltage available to the components or subsystems  130 - 190  when one or more cells of the battery  120  are removed to be subsequently replaced by other cells. 
     The charging unit  130  may be configured to replenish the charge supplied by the battery  120  to power-sinking components or subsystems (e.g., one or more of subsystems  130 - 190 ) or, more specifically, by their associated circuits. To replenish the battery charge, the charging unit  130  may convert one form of electrical energy into another form of electrical energy. More specifically, the charging unit  130  may convert alternating current (AC) to direct current (DC), may perform frequency conversions of current or voltage waveforms, or may convert energy stored in static electric fields or static magnetic fields into direct current. Additionally or alternatively, the charging unit  130  may harvest energy from radiating or evanescent electromagnetic fields (including optical radiation) and convert it into the charge stored in the battery  120 . Furthermore, the charging unit  130  may convert non-electrical energy into electrical energy. For example, the charging unit  130  may harvest energy from motion, or from thermal gradients. 
     The controller  140  may include a processor unit  142  and a memory unit  144 . The processor unit  142  may include one or more processors, such as a microprocessor (μP), a digital signal processor (DSP), a central processing unit (CPU), a graphical processing unit (GPU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or any other suitable electronic processing components. Additionally or alternatively, the processor unit  142  may include photonic processing components. 
     The memory unit  144  may include one or more computer memory devices or components, such as one or more registers, RAM, ROM, EEPROM, or on-board flash memory. The memory unit  144  may use magnetic, optical, electronic, spintronic, or any other suitable storage technology. In some implementations, at least some of the functionality the memory unit  144  may be integrated in an ASIC or and FPGA. Furthermore, the memory unit  144  may be integrated into the same chip as the processor unit  142  and the chip, in some implementations, may be an ASIC or an FPGA. 
     The memory unit  144  may store a smart ring (SR) routine  146  with a set of instructions, that, when executed by the processor  142  may enable the operation and the functionality described in more detail below. Furthermore, the memory unit  144  may store smart ring (SR) data  148 , which may include (i) input data used by one or more of the components  102  (e.g., by the controller when implementing the SR routine  146 ) or (ii) output data generated by one or more of the components  102  (e.g., the controller  140 , the sensor unit  150 , the communication unit  160 , or the user input unit  170 ). In some implementations, other units, components, or devices may generate data (e.g., diagnostic data) for storing in the memory unit  144 . 
     For example, the memory unit  144  may store sensor data collected by the sensor unit  150 . The processor unit  142  may compare sensor data collected at a particular time (e.g., a current heart pattern) to sensor data collected at a previous time (e.g., a previously collected heart pattern or signature) in order to perform various functions. In some implementations, the processor unit  142  may compare sensor data to previously stored sensor data relating to a particular user in order to identify and authenticate the user. In response to authenticating the user, the smart ring  101  may grant the user security access to a digital or physical resource or communicate with another device controlling access to the resource, as discussed in further detail with respect to  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   . In some implementations, in response to authenticating the user, the smart ring  101  may perform a cryptographic operation, as discussed in further detail with respect to  FIG.  5   . 
     The processing unit  142  may draw power from the battery  120  (or directly from the charging unit  130 ) to read from the memory unit  144  and to execute instructions contained in the smart ring routine  146 . Likewise, the memory unit  144  may draw power from the battery  120  (or directly from the charging unit  130 ) to maintain the stored data or to enable reading or writing data into the memory unit  144 . The processor unit  142 , the memory unit  144 , or the controller  140  as a whole may be capable of operating in one or more low-power mode. One such low power mode may maintain the machine state of the controller  140  when less than a threshold power is available from the battery  120  or during a charging operation in which one or more battery cells are exchanged. 
     The controller  140  may receive and process data from the sensors  150 , the communications unit  160 , or the user input devices  170 . The controller  140  may perform computations to generate new data, signals, or information. The controller  140  may send data from the memory unit  144  or the generated data to the communication unit  160  or the output devices  190 . The electrical signals or waveforms generated by the controller  140  may include digital or analog signals or waveforms. The controller  140  may include electrical or electronic circuits for detecting, transforming (e.g., linearly or non-linearly filtering, amplifying, attenuating), or converting (e.g., digital to analog, analog to digital, rectifying, changing frequency) of analog or digital electrical signals or waveforms. 
     The sensor unit  150  may include one or more sensors disposed within or throughout the housing  110  of the ring  101 . Each of the one or more sensors may transduce one or more of: light, sound, acceleration, translational or rotational movement, strain, temperature, chemical composition, surface conductivity or other suitable signals into electrical or electronic sensors or signals. A sensor may be acoustic, photonic, micro-electro-mechanical systems (MEMS) sensors, chemical, micro-fluidic (e.g., flow sensor), or any other suitable type of sensor. 
     The sensors included in the sensor unit  150  may be configured to collect biometric data indicative of biometric signatures unique to an individual user (e.g., wearer) of the ring. For example, the sensor unit  150  may include a heart rate sensor capable of measuring a user&#39;s heart rate. More particularly, the heart rate sensor can measure the electrical activity of the heart by recording an electrocardiogram (ECG), for example. The heart rate sensor may be comprised of one or more electrodes. The collected ECG pattern can be used to identify and authenticate a user because ECG patterns are unique to individuals. Additionally or alternatively, the sensor unit  150  may include other sensors, such as vibration sensors and accelerometers, capable of measuring heart beat signatures. For example, vibration sensors can detect blood flow patterns and/or chest movement patterns which may be indicative of a particular user. The user may need to hold the smart ring  101  against another body part, such as their chest or another hand/finger in order for the sensor unit  150  to collect the biometric data. 
     In some implementations, the sensor unit  150  may include sensors such as accelerometers, gyroscopes, magnetometers, and/or IMUs configured to detect a user&#39;s walking gait. As individuals walk, the movements of their body generally correspond to a signature pattern unique to each individual. The sensor unit  150  of the smart ring  101  can collect motion and orientation data, and may determine the particular pattern of movements that corresponds to the gait of an individual wearer. Subsequently, this collected data may be compared to one or more verified signatures unique to one or more people in order to identify a signature corresponding to the collected data (and to thereby identify a unique identity corresponding to the collected data). 
     The sensor unit  150  may collect other biometric data that may be indicative of a user. For example, the sensor unit  150  may include an iris scanner that can collect images of a user&#39;s eyes. The smart ring  101  may analyze the images to perform iris recognition to identify a user. As another example, the sensor unit  150  may include a fingerprint scanner that can collect fingerprint data unique to a user. Still further, the sensor unit  150  may include acoustic sensors that can collect sound data, such as a user&#39;s voice. The user may speak a password or pass phrase that the smart ring  101  can identify. Additionally or alternatively, the smart ring  101  may perform voice recognition analysis to identify a user. For example, the smart ring  101  may analyze voice parameters, such as pitch, tone, and cadence, to identify the acoustic pattern of the speech. 
     Further, the sensors included in the sensor unit  150  may be configured to collect data indicative of ring movement while a user is wearing the smart ring  101 . For example, the sensor unit  150  may include sensors such as accelerometers, gyroscopes, magnetometers, and/or inertial motion units (IMUs) configured to detect motion and orientation of the smart ring  101 . The sensors can detect combinations of motions that correspond to gestures and patterns of movement made by a wearer of the smart ring  101 . The sensor unit  150  can be equipped with a timer or clock such that detected movements are accompanied by a time stamp. The smart ring  101  can determine, based at least in part upon the closeness in time of detected motions, that a series of detected movements correspond to a gestural pattern. For example, the sensor unit  150  can detect motion corresponding to gestures such as handshakes, fist bumps, knocks, waves, thumbs-up, pointing, and any other hand motions or signals. 
     The sensors in the sensor unit  150  may include tactile sensors that can detect when the smart ring  101 , or when a portion of the smart ring  101  housing including the tactile sensor, comes into contact with another object or device. Examples of tactile sensors include piezoresistive, piezoelectric, capacitive, and elastoresistive sensors. For instance, the tactile sensors may be pressure sensors or strain sensors that can detect when force is applied to the tactile sensor. Similar to how the smart ring  101  can determine, based at least in part upon the closeness in time of detected motions, that a series of detected motion corresponds to a gestural pattern, the smart ring  101  can also determine, based at least in part upon the closeness in time of detected contact, that the contact corresponds to a pattern. For example, the smart ring  101  may detect a sequence of taps (e.g., physical contact between the ring and an object or device) and determine that that the sequence of taps corresponds to a particular pattern of taps. The pattern of taps may be characterized by, for example, an overall number of taps, the time between each tap, the time between a first detected tap and a last detected tap. frequency of taps, tempo of taps, and rhythm of taps. 
     Other sensors of the smart ring  101  besides tactile sensors may also be able to detect when the smart ring  101  makes contact with another device or object. For example, acceleration and/or vibration sensors of the sensor unit  150  may detect sudden changes in acceleration and/or vibration of the smart ring  101  corresponding to contact. 
     Sensors included in the sensor unit  150  may also be able to detect contact with a human body part, such as taps made by a human on the smart ring  101  using a finger. In some cases, these sensors may be user input devices within the user input unit  170 , discussed further below. For example, the smart ring  101  may include specific buttons or portions of the smart ring  101  housing that can detect tactile user input. The sensors may also be used to determine when human skin makes contact with the smart ring  101  or a portion of the smart ring  101  (e.g., the user input unit  170 ) by sensing capacitive coupling or body heat. 
     Still further, sensors of the smart ring  101  may include proximity sensors that can detect when the smart ring  101  is in close proximity to another device. A proximity sensor may also detect contact between the smart ring  101  and another device. For example, if the proximity sensor can detect when the proximity sensor is within a small distance from another device, and if that small distance is on the order of the size of the housing  110 , then a proximity event that that the proximity sensor detects may actually correspond to contact between the housing  110  and another device. The proximity sensors may be capacitive, inductive, magnetic, or optical sensors. 
     As one example, the proximity sensor may detect proximity with another device based at least in part upon short-range communication with the other device. For instance, the smart ring  101  may utilize near field communication (NFC) or other suitable short-range communication standard to detect proximity with another device. The sensor unit  150  (or the communication unit  160 , discussed below) may include an active NFC device (e.g., an NFC chip or tag) that transmits electromagnetic signals from the smart ring  101 . When in close proximity (e.g., on the order of 10 centimeters or less), another NFC-enabled device can receive the signals and respond with signals that the NFC device of the smart ring  101  can detect. The active NFC device may have different modes that allow it to function either in an active mode (e.g., as a scanner or reader) or in a passive mode (e.g., as a tag). Additionally or alternatively, the sensor unit  150  (or the communication unit  160 ) may include a passive NFC device that contains user-specific information that may be accessed by authorized readers. Signals received from an external device may include information including an identifier of the external device, and the smart ring  101  itself may transmit signals including an identifier of the smart ring  101  (e.g., to demonstrate the presence of the smart ring  101  for authentication purposes). As mentioned above, if the NFC-range of the communication unit  160  is on the order of the dimensions of the housing  110 , then detection of NFC communications with another device may actually correspond to physical contact between the smart ring  101  and the other device. 
     The communication unit  160  may facilitate wired or wireless communication between the ring  101  and one or more other devices. The communication unit  160  may include, for example, a network adaptor to connect to a computer network, and, via the network, to network-connected devices. The computer network may be the Internet or another type of suitable network (e.g., a personal area network (PAN), a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a mobile, a wired or wireless network, a private network, a virtual private network, etc.). The communication unit  160  may use one or more wireless protocols, standards, or technologies for communication, such as Wi-Fi, NFC, Bluetooth, or Bluetooth low energy (BLE). Additionally or alternatively, the communication unit  160  may enable free-space optical or acoustic links. In some implementations, the communication unit  160  may include one or more ports for a wired communication connections. The wired connections used by the wireless communication module  160  may include electrical or optical connections (e.g., fiber-optic, twisted-pair, coaxial cable). 
     User input unit  170  may collect information from a person wearing the ring  101  or another user, capable of interacting with the ring  101 . In some implementations, one or more of the sensors in the sensor unit  150  may act as user input devices within the user input unit  170 . User input devices may transduce tactile, acoustic, video, gesture, or any other suitable user input into digital or analog electrical signal, and send these electrical signals to the controller  140 . 
     The output unit  190  may include one or more devices to output information to a user of the ring  101 . The one or more output devices may include acoustic devices (e.g., speaker, ultrasonic); haptic (thermal, electrical) devices; electronic displays for optical output, such as an organic light emitting device (OLED) display, a laser unit, a high-power light-emitting device (LED), etc.; or any other suitable types of devices. For example, the output unit  190  may include a projector that projects an image onto a suitable surface. In some implementations, the sensor unit  150 , the user input unit  170 , and the output unit  190  may cooperate to create a user interface with capabilities (e.g., a keyboard) of much larger computer systems, as described in more detail below. 
     Devices external to the smart ring  101  may support the user input and/or output functionalities of the smart ring  101 . For example, in some implementations, the smart ring  101  may receive user input and/or output information to a user through a communicative connection with another device, such as the user device  104  or the mobile device  106 . The smart ring  101  may pair with these devices, for example via a Wi-Fi, NFC, Bluetooth, or other suitable wireless or wired communicative connection, and a user may be able to pass information to the smart ring  101  by interacting with the paired device. For instance, the paired device may display a webpage or application associated with the smart ring  101 . The user may input information via the webpage or application, and the paired device may communicate this user input to the smart ring  101 . When the smart ring  101  has information for the user and/or has a request to display to the user, the smart ring  101  may communicate this information and/or request to the paired device, and the paired device may output the information and/or request to the user. 
     The components  120 ,  130 ,  140 ,  150 ,  160 ,  170 , and/or  190  may be interconnected by a bus  195 , which may be implemented using one or more circuit board traces, wires, or other electrical, optoelectronic, or optical connections. The bus  195  may be a collection of electrical power or communicative interconnections. The communicative interconnections may be configured to carry signals that conform to any one or more of a variety of protocols, such as I2C, SPI, or other logic to enable cooperation of the various components. 
       FIG.  2    includes block diagrams of a number of different example form factor types or configurations  205 A,  205 B,  205 C,  205 C,  205 D,  205 E, and/or  205 F of a smart ring (e.g., the smart ring  101 ). The configurations  205 A,  205 B,  205 C,  205 C,  205 D,  205 E, and/or  205 F (which may also be referred to as the smart rings  205 A,  205 B,  205 C,  205 C,  205 D,  205 E, and/or  205 F) may each represent an implementation of the smart ring  101 , and each may include any one or more of the components  102  (or components similar to the components  102 ). In some embodiments, one or more of the components  102  may not be included in the configurations  205 A,  205 B,  205 C,  205 C,  205 D,  205 E, and/or  205 F. The configurations  205 A,  205 B,  205 C,  205 C,  205 D,  205 E, and/or  205 F include housings  210 A,  210 B,  210 C,  210 C,  210 D,  210 E, and/or  210 F, which may be similar to the housing  110  shown in  FIG.  1   . 
     The configuration  205   a  may be referred to as a band-only configuration comprising a housing  210   a . In the configuration  205   b , a band may include two or more removably connected parts, such as the housing parts  210   b  and  210   c . The two housing parts  210   b  and  210   c  may each house at least some of the components  102 , distributed between the housing parks  210   b  and  210   c  in any suitable manner. 
     The configuration  205   c  may be referred to as a band-and-platform configuration comprising (i) a housing component  210   d  and (ii) a housing component  210   e  (sometimes called the “platform  210   e ”), which may be in a fixed or removable mechanical connection with the housing  210   d . The platform  210   e  may function as a mount for a “jewel” or for any other suitable attachment. The housing component  210   d  and the platform  210   e  may each house at least one or more of the components  102  (or similar components). 
     In some instances, the term “smart ring” may refer to a partial ring that houses one or more components (e.g., components  102 ) that enable the smart ring functionality described herein. The configurations  205   d  and  205   e  may be characterized as “partial” smart rings, and may be configured for attachment to a second ring. The second ring may be a conventional ring without smart functionality, or may be second smart ring, wherein some smart functionality of the first or second rings may be enhanced by the attachment. 
     The configuration  205   d , for example, may include a housing  210   f  with a groove to enable clipping onto a conventional ring. The grooved clip-on housing  210   f  may house the smart ring components described above. The configuration  205   e  may clip onto a conventional ring using a substantially flat clip  210   g  part of the housing and contain the smart ring components in a platform  210   h  part of the housing. 
     The configuration  205   f , on the other hand, may be configured to be capable of being mounted onto a finger of a user without additional support (e.g., another ring). To that end, the housing  210   i  of the configuration  205   f  may be substantially of a partial annular shape subtending between 180 and 360 degrees of a full circumference. When implemented as a partial annular shape, the housing  210   i  may be more adaptable to fingers of different sizes that a fully annular band (360 degrees), and may be elastic. A restorative force produced by a deformation of the housing  210   i  may ensure a suitable physical contact with the finger. Additional suitable combinations of configurations (not illustrated) may combine at least some of the housing features discussed above. 
       FIG.  3    includes perspective views of example configurations  305   a ,  305   b ,  305   c ,  305   c ,  305   d ,  305   e , and/or  305   f  of a smart right (e.g., the smart ring  101 ) in which a number of surface elements are included. 
     Configuration  305   a  is an example band configuration  205   a  of a smart ring (e.g., smart ring  101 ). Some of the surface elements of the housing may include interfaces  312   a ,  312   b  that may be electrically connected to, for example, the charging unit  130  or the communications unit  160 . On the outside of the configuration  305   a , the interfaces  312   a ,  312   b  may be electrically or optically connected with a charger to transfer energy from the charger to a battery (e.g., the battery  120 ), or with another device to transfer data to or from the ring  305   a . The outer surface of the configuration  305   a  may include a display  390   a , while the inner surface may include a biometric sensor  350   a.    
     The configurations  305   b  and  305   c  are examples of configurations of a smart ring with multiple housing parts (e.g., configuration  205   b  in  FIG.  2   ). Two (or more) parts may be separate axially (configuration  305   b ), azimuthally (configuration  305   c ), or radially (nested rings, not shown). The parts may be connected mechanically, electrically, or optically via, for example, interfaces analogous to interfaces  312   a ,  312   b  in configuration  305   a . Each part of a smart ring housing may have one or more surface elements, such as, for example, sensors  350   b ,  350   c  or output elements  390   b ,  390   c . The latter may be LEDs (e.g., output element  390   b ) or haptic feedback devices (e.g., output element  390   c ), among other suitable sensor or output devices. Additionally or alternatively, at least some of the surface elements (e.g., microphones, touch sensors) may belong to the user input unit  170 . 
     Configuration  305   d  may be an example of a band and platform configuration (e.g., configuration  205   c ), while configurations  305   e  and  305   f  may be examples of the partial ring configurations  205   d  and  205   e , respectively. Output devices  390   d ,  390   e , and  390   f  on the corresponding configurations  305   d ,  305   e , and  305   f  may be LCD display, OLED displays, e-ink displays, one or more LED pixels, speakers, or any other suitable output devices that may be a part of a suite of outputs represented by an output unit (e.g., output unit  190 ). Other surface elements, such as an interface component  312   c  may be disposed within, at, or through the housing. It should be appreciated that a variety of suitable surface elements may be disposed at the illustrated configurations  305   a ,  305   b ,  305   c ,  305   c ,  305   d ,  305   e , and/or  305   f  at largely interchangeable locations. For example, the output elements  390   d ,  390   e , and  390   f  may be replaced with sensors (e.g., UV sensor, ambient light or noise sensors, etc.), user input devices (e.g., buttons, microphones, etc.), interfaces (e.g., including patch antennas or optoelectronic components communicatively connected to communications units), or other suitable surface elements. 
       FIG.  4    illustrates an example environment  400  within which a smart ring  405  may be configured to operate. In an embodiment, the smart ring  405  may be the smart ring  101 . In some embodiments, the smart ring  405  may be any suitable smart ring capable of providing at least some of the functionality described herein. Depending on the embodiment, the smart ring  405  may be configured in a manner similar or equivalent to any of the configurations  205 A,  205 B,  205 C,  205 C,  205 D,  205 E, and/or  205 F or  305   a ,  305   b ,  305   c ,  305   c ,  305   d ,  305   e , and/or  305   f  shown in  FIG.  2    and  FIG.  3   . 
     The smart ring  405  may interact (e.g., by sensing, sending data, receiving data, receiving energy) with a variety of devices, such as bracelet  420  or another suitable wearable device, a mobile device  422  (e.g., a smart phone, a tablet, etc.) that may be, for example, the user device  104 , another ring  424  (e.g., another smart ring, a charger for the smart ring  405 , etc.), a secure access panel  432 , a golf club  434  (or another recreational accessory), a smart ring  436  worn by another user, or a steering wheel  438  (or another vehicle interface). Additionally or alternatively, the smart ring  405  may be communicatively connected to a network  440  (e.g., WiFi, 5G cellular), and by way of the network  440  (e.g., network  105  in  FIG.  1   ) to a server  442  (e.g., server  107  in  FIG.  1   ) or a personal computer  444  (e.g., mobile device  106 ). Additionally or alternatively, the ring  405  may be configured to sense or harvest energy from natural environment, such as the sun  450 . 
     The secure access panel  432 , for example, may control access to a resource. The smart ring  101  may interact with the secure access panel  432  in order to cause the secure access panel  432  to grant the wearer and/or the smart ring  101  access to the resource. For example, the secure access panel  432  may include a lock that controls access to a physical resource or physical space such as a home, room, vehicle, safe, etc. 
     The ring  405  may exchange data with other devices by communicatively connecting to the other devices using, for example, the communication unit  160 . The communicative connection to other device may be initiated by the ring  405  in response to user input via the user input unit  170 , in response to detecting trigger conditions using the sensor unit  150 , or may be initiated by the other devices. The communicative connection may be wireless, wired electrical connection, or optical. In some implementation, establishing a communicative link may include establishing a mechanical connection. 
     The ring  405  may connect to other devices (e.g., a device with the charger  103  built in) to charge the battery  120 . The connection to other devices for charging may enable the ring  405  to be recharged without the need for removing the ring  405  from the finger. For example, the bracelet  420  may include an energy source that may transfer the energy from the energy source to battery  120  of the ring  405  via the charging unit  430 . To that end, an electrical (or optical) cable may extend from the bracelet  420  to an interface (e.g., interfaces  112   a ,  112   b ,  312   a ,  312   b ) disposed at the housing (e.g., housings  110 ,  210   a ,  210   b ,  210   c ,  210   d ,  210   e ,  210   f ,  210   g ,  210   h , and/or  210   i ) of the ring  405 . The mobile device  422 , the ring  424 , the golf club  434 , the steering wheel  438  may also include energy source configured as chargers (e.g., the charger  103 ) for the ring  405 . The chargers for may transfer energy to the ring  405  via a wired or wireless (e.g., inductive coupling) connection with the charging unit  130  of the ring  405 . 
     Security Implementations 
     The smart ring  101  may be used to perform a variety of security-related functions. Within the general category of security are three-interrelated concepts: identification, authentication, and authorization. As will be described herein, the smart ring  101  can perform functions related to each of these three concepts. Identification relates to determining who a user is, e.g., to answering the question, “Who are you?” As an example, a user of a computing system may provide a username that indicates an identity of the user. Authentication relates to determining whether the user is who the user said to be. Continuing with the previous example, a user of a computing system may provide a password associated with the username that proves the user is indeed the user associated with the username. Authorization relates to granting a user access to a resource and/or performing a function a user has requested in response to the user being both (1) identified and (2) authenticated. 
     Authentication may be based at least in part upon one or more factors. Example authentication factors include: knowledge factors (e.g., something a user knows, such as a password or personal identification number (PIN)), possession factors (e.g., something a user has, such as a physical key or card, or a token device that produces temporary passwords or PINs), or inherence factors (e.g., something a user is, such as a biometric signature of the user). Multi-factor authentication relies on a combination of multiple authentication factors. In the context of the present disclosure, the smart ring  101  may support authentication factors within all three categories (knowledge, possession, and inherence), as will be discussed with reference to  FIG.  5   ,  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   . As a first example, the smart ring  101  may collect biometric data that facilitates biometric authentication. Further, the smart ring  101  itself may be a token that, if the user demonstrates possession of the smart ring  101 , serves as a possession authentication factor. The smart ring  101  can also verify the proximity of other tokens to the smart ring  101 . Moreover, the smart ring  101  can collect PINs/passwords from the user, determine gestural patterns performed by the user, and determine contact patterns (e.g., coded knocks) performed by the user, facilitating authentication based at least in part upon knowledge factors. 
       FIG.  5    illustrates an example method  500  for identifying and authenticating a user using biometric data collected by the smart ring  101  according to one embodiment. In the example method  500 , the smart ring  101  performs an authentication operation using an authentication factor corresponding to biometric data. In some implementations, the method  500  can begin at block  502 . In other implementations, the method  500  may begin at block  506 . 
     At block  502 , sensors of the smart ring  101  (e.g., sensor unit  150 ) collect biometric data of a user during an enrollment or set-up mode of the smart ring  101 . The smart ring  101  may enter an enrollment mode in order to register a new user to utilize the smart ring  101 , or to update a profile of an existing known user of the smart ring  101 . During the enrollment mode, a user may provide an identification to the smart ring  101  besides the biometric data, in order for the smart ring  101  to associate the collected biometric data with a particular identity. For instance, the user may set up a profile on the smart ring  101  itself or by pairing the smart ring  101  with another device, such as the mobile device  422  or the mobile device  106 . The user may provide a username associated with the user and/or some other suitable form of identification such that the smart ring  101  can associate biometric data collected during the enrollment mode to an identified, known user. As will be described with reference to  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   , other data, such as gestural data, proximity data, and contact data, may also be collected during the enrollment mode and associated with an identified, known user. 
     At block  504 , the smart ring  101  determines a biometric signature of the identified user based at least in part upon the biometric data collected during the enrollment mode and stores the biometric signature. The smart ring  101  may determine the biometric signature using the controller  140 . Additionally or alternatively, the smart ring  101  may communicate all or a portion of the collected biometric data to the server  107 , the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 , which may in turn perform the analysis to determine the biometric signature. In some cases, no processing may be needed to determine the biometric signature; the biometric data may simply be stored as-is (e.g., as collected by the sensor unit  150 ). In other cases, the analyzing device (whether it is the smart ring  101  or an external device) may determine parameters and/or patterns based at least in part upon the biometric data and assign these parameters and/or patterns as the biometric signature. In any case, the biometric signature is unique to a particular user. 
     As an example, the smart ring  101  may collect an ECG of the identified user. The analyzing device can determine features of the ECG, such as the types of waves within the ECG (e.g., P, Q, R, S, and/or T waves), the locations and intervals among the waves, the amplitude of the waves, the shapes of the waves, the frequency, etc. A set of ECG features for a particular user may be unique when compared to sets of ECG features for other users (thus, the sets of ECG features may function as unique signatures). The specific ECG pattern and/or the identified features of the ECG pattern then can be stored as a biometric signature. Similarly, as another example, the smart ring  101  may collect motion and orientation data while a user walks. The analyzing device may determine that the motion and orientation data correspond to a user walking, and may identify a specific movement pattern within the motion and orientation data corresponding to the user&#39;s gait. The specific movement pattern can then be stored as a biometric signature. 
     Other biometric data that the smart ring  101  can collect and can determine a corresponding biometric signature for include: a fingerprint, an iris scan, or voice data. For instance, the smart ring  101  may identify a specific acoustic pattern associated with the identified user&#39;s speech and store this acoustic pattern as a biometric signature. 
     The analyzing device itself may store the biometric signature. In some implementations, the analyzing device may communicate the biometric signature to the smart ring  101 , and the smart ring  101  may store the biometric signature on the memory unit  144 . Alternatively or in addition, the analyzing device may communicate the biometric signature to the server  107 , which may function as an authentication server, as mentioned previously. 
     At block  506 , sensors of the smart ring  101  collect, outside the enrollment mode, biometric data of a particular user while the particular user is wearing the smart ring. As discussed previously with respect to  FIG.  1    and the sensor unit  150 , the sensors of the sensor unit  150  can collect a variety of biometric data that may be indicative of a biometric signature, such as heartbeat pattern, walking gait, fingerprint, iris, and/or voice data. In the example method  500 , the collected biometric data includes a heartbeat pattern of the user. For example, the heartbeat pattern may be a heart rate (e.g., pulse rate), an ECG, and/or physical movement data corresponding to the heartbeat pattern (e.g., chest vibrations corresponding to a heartbeat pattern, blood flow patterns corresponding to a heartbeat pattern). 
     The smart ring  101  may constantly collect biometric data in order to determine that the wearer is an authenticated user. The smart ring  101  may collect biometric data at regular periods (e.g., after several seconds, minutes, or hours of wear by a user). Alternatively or additionally, the smart ring  101  may collect biometric data in response to a request from the user to perform an operation or in response to receiving a signal from another device. For example, when the smart ring  101  is brought into proximity with a secure access panel  432  (e.g., proximity close enough for NFC communication), the secure access panel  432  may transmit a signal to the smart ring  101  indicating that the smart ring  101  must provide identification and authentication of the wearer in order to receive authorization to open the secure access panel  432 . 
     As another example, the user may wish to perform a cryptographic operation, as will be discussed in more detail below with reference to block  512 . The user may need a cryptographic key stored on the smart ring  101  in order to perform the cryptographic operation. The user may indicate to the smart ring  101  that they wish to perform the cryptographic operation, for example by interacting with the user input unit  170  (e.g., by pressing a button or screen on the smart ring  101  or on a paired device). Following the request, the smart ring  101  performs an authentication operation in order to authenticate the user as an identified user associated with the cryptographic key before releasing the cryptographic key. 
     At block  508  and block  510 , the smart ring  101  performs an authentication operation by (i) comparing the biometric data to a biometric signature for a known user to determine whether the biometric data matches the biometric signature (block  508 ), and (ii) when the biometric data matches the biometric signature, authenticating the particular user by updating a record to indicate that the particular user has been identified and authenticated as the known user (block  510 ). 
     More particularly, at block  508 , the smart ring  101  compares the biometric data collected at block  506  to a biometric signature for a known user to determine whether the biometric data matches the biometric signature. If optional steps  502  and  504  have not been performed, the smart ring  101  may compare the biometric data to biometric signatures included in a general database of biometric signatures for known individuals stored externally, such as at the server  107 . In implementations where steps  502  and  504  have been performed, then the biometric data are compared to the biometric signature collected while the smart ring  101  was in an enrollment mode. The biometric signature may be stored at the smart ring  101 , such as in the memory unit  144 , or may be stored on an external device such as the server  107 , the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 . In implementations where the biometric signature is stored at a device external to the smart ring  101 , the smart ring  101  may communicate all or a portion of the collected biometric data to the external device in order to facilitate comparison. 
     The external device or the smart ring  101  then compares the biometric data to the stored biometric signature. The stored biometric signature is associated with a previously identified, known user. If the smart ring  101  causes the external device to perform the comparison, the external device can communicate the results of the comparison to the smart ring  101 . 
     The collected biometric data and the stored biometric signature do not need have to match exactly. The smart ring  101  can determine that the collected biometric data and the stored biometric signature match if the two data sets are similar within a tolerance or threshold suitable for the particular biometric application. For instance, the tolerance may be based at least in part upon the uncertainty of the biometric measurement, which may depend on the sensors that collect the biometric data. 
     As an example, if the collected biometric data includes a heartbeat pattern, then the collected heartbeat pattern is compared to a biometric signature, such as a stored ECG or stored features of the ECG. The comparison may be between the collected heartbeat pattern and the stored ECG. Alternatively or in addition, the external device or the smart ring  101  may identify certain features of the heartbeat pattern (e.g., the features of the waves within the ECG, as mentioned previously) and compare these identified features to the stored features of the ECG. If the collected heartbeat pattern matches the biometric signature, or at least matches within a tolerance, then the smart ring  101  determines that the wearer of the ring has the identity associated with the biometric signature and has authenticated the identity by providing the biometric data. 
     As another example, if the collected biometric data includes motion data corresponding to a walking gait, then the motion data are compared to stored walking gait data. The comparison may be between the collected motion data and the stored walking gait data. Alternatively or in addition, the external device or the smart ring  101  may identify certain features of the walking gait (e.g., a specific pattern of motion) and compare these features to the features of the stored walking gait. 
     At block  510 , when the biometric data matches the biometric signature, the smart ring  101  authenticates the user by updating a record to indicate that the user has been identified and authenticated as the known user associated with the biometric signature. If the collected biometric data matches a biometric signature, then the smart ring  101  has both (1) identified the particular user as the known user associated with the biometric signature, and (2) authenticated the particular user to actually be the known user associated with the biometric signature. 
     The smart ring  101  updates the record by recording in the memory unit  144  an indication of the positive match between the collected biometric data and the biometric signature. The record, for example, may correspond to a location in the memory unit  144  that devices external to the smart ring  101  and/or components internal to the smart ring  101 , such as the processor unit  142 , can query to determine whether the user is authenticated. Alternatively or in addition, whenever the controller  140  determines that the record has been updated to reflect that an authentication operation has been performed, the controller  140  can communicate this update to devices and/or components external or internal to the smart ring  101  (e.g., by transmitting a signal). 
     The update to the record may indicate why the smart ring  101  determined that the user has been authenticated (e.g., the record may indicate that collected biometric data matched a biometric signature), or the update to the record may indicate that the current wearer of the ring is an authenticated user, e.g., that the smart ring  101  is in an authenticated state. If the sensor unit  150  determines that the user has removed the smart ring  101  from their finger (e.g., because the sensor unit  150  can no longer detect any pulse, much less a specific heartbeat pattern), then the smart ring  101  may update the record to indicate that the smart ring  101  is no longer in an authenticated state. 
     If the smart ring  101  determines that the collected biometric data does not match the biometric signature, then the smart ring  101  may not update the record at all, or may update the record to indicate that a failed authentication operation has occurred. If the smart ring  101  detects a failed authentication (whether a biometric authentication operation, a gestural authentication operation as described with reference to  FIG.  6 A , or a proximity authentication operation as described with reference to  FIG.  6 B  and  FIG.  7   ), the smart ring  101  will not authenticate the user. The smart ring  101  may communicate (e.g., via output unit  190  or a paired device) to the user that the user has not been authenticated or that an authentication operation has failed. The smart ring  101  may prompt the user to re-authenticate themselves, for example, by putting the smart ring  101  back on a finger or performing an authentication gesture. 
     Note, while the example method  500  authenticates the wearer of the smart ring  101  using biometric data including a heartbeat pattern of the wearer, other implementations may include additional authentication operations. For example, the smart ring  101  may authenticate the wearer using gestural data, proximity data, or a combination thereof, using techniques described with reference to  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   . The smart ring  101  may also authenticate the wearer by requesting a PIN number or password from the wearer (e.g., via the output unit  190 ) and comparing a user-provided PIN number or password to a PIN number or password stored on the smart ring  101 . After each authentication operation, the smart ring  101  can update the record to indicate that the wearer has been authenticated based at least in part upon the authentication operation. The smart ring  101  may also update the record after the wearer has been authenticated as the known user based at least in part upon more than one authentication operation. Different applications may need that the wearer be authenticated based at least in part upon more than one authentication operation. For example, if an application needs that the user be authenticated using two authentication factors, and a first authentication operation succeeds in authenticating the user based at least in part upon a first authentication factor while a second authentication operation fails to authenticate the user based at least in part upon a second authentication factor, then the user may not be authenticated or may not be allowed to access the application. 
     As one example, the smart ring  101  may repeat steps  504 ,  506 ,  508 . and  510  before performing step  512  using additional biometric data. As mentioned above, the smart ring  101  may, in addition to collecting a heartbeat pattern, also collect data corresponding to a walking gait of the user. The collected walking gait may be compared to a biometric signature corresponding to a walking gait pattern of a known user in order to determine whether the collected walking gait matches the biometric signature. If so, then the smart ring  101  can update the record to indicate that the user has been identified and authenticated as the known user based at least in part upon walking gait. In such implementations, the smart ring  101  may perform step  512  only after the record indicates that the user has been authenticated as the known user based at least in part upon both heartbeat pattern data and walking gait pattern data. 
     At block  512 , when the record indicates that the user has been identified and authenticated, the smart ring  101  performs a cryptographic operation, such as digitally signing transaction data using a cryptographic key stored on the memory unit  144  of the smart ring  101 . As mentioned previously, the smart ring  101  may perform steps  506 ,  508 ,  510 , and  512  in response to a specific request by the user to perform a cryptographic operation. In response to the smart ring  101  identifying and authenticating the user, and reflecting this authentication by updating the record, the smart ring  101  can then perform the cryptographic operation. In other words, by updating the record, the smart ring  101  (i) indicates that the user has been identified and authenticated as a known user and (ii) grants authorization to the user to access the cryptographic keys associated with the known user and stored on the smart ring  101 . As mentioned previously, while example method  500  authenticates the user based at least in part upon biometric data, in other implementations, step  512  may only be performed after the user is authenticated based at least in part upon multiple authentication operations. 
     A transaction may refer to any exchange of data, information, or currency, including cryptocurrency such as Bitcoin. While referred to as an “exchange,” it is understood that the transaction may comprise one-way output rather than a two-way exchange. Conventionally, information related to transactions are stored in centralized databases held by participants of the transactions or third-party arbiters. However, the transaction data that the smart ring digitally signs or encrypts with a private key can be transaction data of a blockchain. Below is a brief discussion of a blockchain and the secure transactions that the blockchain may facilitate. 
     A blockchain (e.g., an example of a distributed ledger) is a way of achieving a distributed consensus on the validity or invalidity of information in the chain. In other words, the blockchain provides a decentralized trust to participants and observers. As opposed to relying on a central authority, a blockchain is a decentralized database in which a transactional record of changes to the ledger is maintained and validated by each node of a peer-to-peer network. The distributed ledger is comprised of groupings of transactions organized together into a “block,” and ordered sequentially (thus the term “blockchain”). 
     The nodes that share the ledger form what is referred to herein the distributed ledger network. The nodes in the distributed ledger network validate changes to the blockchain (e.g., when a new transaction and/or block is created) according to a set of consensus rules. The consensus rules depend on the information being tracked by the blockchain and may include rules regarding the chain itself. For example, a consensus rule may include that the originator of a change supplies a proof-of-identity such that only approved entities may originate changes to the chain. A consensus rule may need that blocks and transactions adhere to format need and supply certain meta information regarding the change (e.g., blocks must be below a size limit, transactions must include a number of fields, etc.). Consensus rules may include a mechanism to determine the order in which new blocks are added to the chain (e.g., through a proof-of-work system, proof-of-stake, etc.). 
     Additions to the blockchain that satisfy the consensus rules are propagated from nodes that have validated the addition to other nodes that the validating node is aware of. If all the nodes that receive a change to the blockchain validate the new block, then the distributed ledger reflects the new change as stored on all nodes, and it may be said that distributed consensus has been reached with respect to the new block and the information contained therein. Any change that does not satisfy the consensus rule is disregarded by validating nodes that receive the change and is not propagated to other nodes. Accordingly, unlike a traditional system which uses a central authority, a single party cannot unilaterally alter the distributed ledger unless the single party can do so in a way that satisfies the consensus rules. The inability to modify past transactions leads to blockchains being generally described as trusted, secure, and immutable. 
     The validation activities of nodes applying consensus rules on a blockchain network may take various forms. In one implementation, the blockchain may be viewed as a shared spreadsheet that tracks data such as the ownership of assets. In another implementation, the validating nodes execute code contained in “smart contracts” and distributed consensus is expressed as the network nodes agreeing on the output of the executed code. 
     When entities communicate with nodes of the blockchain to initiate or to add data to a smart contract or secure transaction, the transaction may be accompanied by a proof-of-identity of the entity. The cryptographic proof-of-identity can be included in transactions sent to the blockchain. For example, each entity (e.g., a particular user) may own private cryptographic keys that are associated with public cryptographic keys known to belong to the entity (e.g., public cryptographic keys associated with each of the entities may be published by a trusted third party or proven to other network participants, etc.). The private cryptographic key may be, for example, a unique alphanumeric string of numbers and letters generated by a random number generator. An entity wishing to send a transaction to the blockchain may sign a cryptographic message in the transaction with the entity&#39;s private cryptographic key to prove the identity of the entity sending the transaction. In this way, other network participants may be provided with cryptographic proof that the information contained in the transaction was originated by the participating entity. 
     Returning to  FIG.  5   , at block  512 , if the smart ring  101  identifies and authenticates the user as a known user, then the smart ring may sign (e.g., encrypt) transaction data with the private cryptographic keys of the known user. A known user&#39;s private cryptographic keys may be stored on the memory unit  144  of the smart ring  101 . The private cryptographic keys are associated with the known user and no other user. Thus, the smart ring  101  must identify and authenticate the user as the known user before signing transaction data with the known user&#39;s private cryptographic keys. 
     The smart ring  101  may generate private cryptographic keys and store the keys on the memory unit  144 . In some instances, the smart ring  101  may generate a key for the known user in response to authenticating the user as the known user. The smart ring  101  may generate the private key using a random number generator according to a seed value securely stored on the smart ring. The seed value is a number that is unique to the known user. During an enrollment or set-up mode, a known user may enter a seed value into the smart ring  101  using a paired device or the user input unit  170 . Alternatively, the known user may enter a seed phrase that the smart ring  101  translates into a corresponding seed value. Further, the smart ring  101  may generate the seed value and/or seed phrase for the known user. The smart ring  101  may associate the seed value and/or seed phrase with the known user, for example by securely storing the seed value and/or seed phrase in a profile of the known user. 
     The smart ring  101  may sign the transaction data in a variety of ways. For example, the transaction data itself may be communicated to the smart ring  101  by an external computing device. The smart ring  101  then can sign the received transaction data locally at the smart ring  101 . In other scenarios, the smart ring may communicate with an external computing device, which may be a blockchain node or may be another device, such as the user device  104 , in communicative connection with a blockchain, to digitally sign the transaction data. 
     The transaction data may correspond to any transaction facilitated by a blockchain. For example, the transaction data may be a smart contract. A smart contract is a computer protocol that enables the automatic execution and/or enforcement of an agreement between different parties. The smart contract may be computer code that is located at a particular address on a blockchain. The smart contract may include one or more trigger conditions that, when satisfied, correspond to one or more actions. For some smart contracts, the actions performed may be determined based at least in part upon one or more decision conditions. In some instances, data streams may be routed to the smart contract so that the smart contract may detect that a trigger condition has occurred and/or analyze a decision condition. 
     The user may seek to initiate or create a smart contract and deploy the smart contract on the blockchain, or the user may need to add information to a deployed smart contract. The user may update or create the smart contract using a device communicatively connected to a blockchain network, such as the smart ring  101  or another external device, such as the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 . The smart ring  101  operates to encrypt the smart contract by digitally signing the smart contract using a private cryptographic key of the known user once the user is authenticated as the known user. 
     As another example, the transaction data may relate to a cryptocurrency transaction, such as a Bitcoin transaction. The particular user may seek to transfer cryptocurrency to an address on a blockchain. To confirm the transaction, the particular user signs the transaction with a private key. As in the case of the smart contract, the smart ring  101  signs the cryptocurrency transaction using a private cryptographic key of the known user once the user is authenticated as the known user. 
     After authenticating the wearer as the known user, the smart ring  101  may perform other cryptographic operations and/or security functions. For example, the smart ring  101  may decrypt transaction data using a private or public cryptographic key. The smart ring  101  may also grant authorization to the user to access digital and/or physical resources. Further examples of the security functions of the smart ring  101  can perform are discussed herein with reference to  FIG.  6 A ,  FIG.  6 B , and  FIG.  7   . It should be understood that the various authentication techniques (e.g., authentication based at least in part upon biometric, gestural, or proximity data) can be combined to perform any combination of the operations discussed herein (e.g., unlocking a resource or performing a cryptographic operation). 
       FIG.  6 A  and  FIG.  6 B  illustrate an example method  600  for performing multi-factor authentication using the smart ring  101  according to one embodiment. In some implementations, the method  600  can begin at block  602 . In other implementations, the method  600  may begin at block  606 . 
     In the example method  600 , the smart ring  101  performs multi-factor authentication using (i) a first authentication factor corresponding to a gesture, and (2) a second authentication factor corresponding to contact between the smart ring  101  and a component external to the smart ring. While example method  600  includes two authentication factors, the smart ring  101  is capable of performing additional authentication operations using additional, different authentication factors. 
     Beginning with  FIG.  6 A , at block  602 , the sensors of the sensor unit  150  collect gestural data of a user during an enrollment mode or set-up mode of the smart ring  101 . The smart ring  101  may perform block  602  in a manner similar to block  502 . The smart ring  101  may enter an enrollment mode in order to register a new user to utilize the smart ring  101 , or to update a profile of an existing known user of the smart ring  101 . During the enrollment mode, a user may provide an identification to the smart ring  101  besides the gestural data, in order for the smart ring  101  to associate the collected gestural data with a particular identity. For instance, the user may set up a profile on the smart ring  101  itself or by paring the smart ring  101  with another device, such as the mobile device  422  or the mobile device  106 . The user may provide a username associated with the user and/or some other suitable form of identification such that the smart ring  101  can associate gestural data collected during the enrollment mode to an identified, known user. During the same enrollment mode, the smart ring  101  may collect both gestural and biometric data. 
     While the smart ring  101  is in the enrollment mode, the user can perform a specific gesture that the user wishes to associate with their identity. The smart ring  101  may itself prompt the user to perform the gesture (e.g., via output unit  190 ) or the user device  104  or the mobile device  106  paired with the smart ring  101  may prompt the user. In this way, the smart ring  101  can determine that motion and movement data collected directly after the prompt is to be associated with a specific gesture. The smart ring  101  may prompt the user to perform the gesture several times in order for the smart ring  101  to identify the gestural pattern. 
     At block  604 , the smart ring  101  determines an authentication gesture of the identified user based at least in part upon the gestural data collected during the enrollment mode and stores the authentication gesture. The smart ring  101  may determine the authentication gesture using the controller  140 . Additionally or alternatively, the smart ring  101  may communicate all or a portion of the collected gestural data to the server  107 , the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 , which may in turn perform the analysis to determine the authentication gesture. In some cases, no processing may be needed to determine the authentication gesture; the gestural data (e.g., the motion and orientation data corresponding to the gesture) may simply be stored as-is (e.g., as collected by the sensor unit  150 ). In other cases, the analyzing device (whether it is the smart ring  101  or an external device) may determine parameters and/or patterns based at least in part upon the gestural data and assign these parameters and/or patterns as the authentication gesture. In any case, the authentication gesture is associated with the particular identified user. 
     As an example, the smart ring  101  may collect motion and orientation data of the identified user during the enrollment mode while the identified user performs a secret gesture known only to the identified user. The analyzing device can determine the specific pattern of movement and orientation of the collected data, and classify this specific pattern as an authentication gesture associated with the identified user. This specific pattern can then be stored as an authentication gesture. 
     The analyzing device itself may store the authentication gesture. In some implementations, the analyzing device may communicate the authentication gesture to the smart ring  101 , and the smart ring  101  may store the authentication gesture on memory unit  144 . Alternatively or in addition, the analyzing device may communicate the authentication gesture to the server  107 , which may function as an authentication server, as mentioned previously. 
     At blocks  606 ,  608 ,  610 , and  612 , the smart ring  101  performs a first authentication operation. Beginning at block  606 , the sensor unit  150  collects, outside of the enrollment mode, gestural data representing a candidate gesture and a first authentication factor. The candidate gesture corresponds to ring movement while a user is wearing the smart ring. The gestural data includes motion and orientation data collected by the sensor unit  150 . 
     The smart ring  101  may collect the gestural data in response to a request from the user made using the user input unit  170 . For example, the user may indicate to the smart ring  101  that the smart ring  101  should authenticate the user as a known user so that the user may access a particular resource. Alternatively, the smart ring  101  may collect the gestural data in response to receiving a signal from a second device external to the smart ring  101 . The second device controls access to a physical or digital resource. For example, the second device may correspond to the secure access panel  432  controlling access to a physical resource. As another example, the second device may be a device that controls access to digital information, such as the mobile device  422 , the server  442 , the personal computer  444 , or another smart ring  436  or other wearable device worn by another user. When the smart ring  101  is in proximity to the second device, the second device may transmit a signal to the smart ring  101  indicating that the smart ring  101  should authenticate the wearer of the smart ring  101  in order to access the resource. The smart ring  101  may indicate to the user (e.g., via the output unit  190 ) that the user should perform an authentication gesture in order to authenticate themselves. 
     The smart ring  101  (or a separate analyzing device, in a manner analogous to block  604 ) can determine a pattern of movement and orientation of the collected gestural data which corresponds to a candidate gesture. At block  608 , the smart ring  101  compares candidate gesture to an authentication gesture for a known user to determine whether the candidate gesture matches the authentication gesture. If optional steps  602  and  604  have not been performed, the smart ring  101  may compare the candidate gesture to authentication gestures included in a general database of authentication gestures for known individuals stored externally, such as at the server  107 . In implementations where steps  602  and  604  have been performed, then the candidate gesture is compared to the authentication gesture collected while the smart ring  101  was in an enrollment mode. The authentication gesture may be stored at the smart ring  101 , such as in the memory unit  144 , or may be stored on an external device such as the server  107 , the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 . In implementations where the authentication gesture is stored at a device external to the smart ring  101 , the smart ring  101  may communicate all or a portion of the collected gestural data to the external device in order to facilitate comparison between the candidate gesture and the authentication gesture. 
     The external device or the smart ring  101  then compares the candidate gesture to the stored authentication gesture. The stored authentication gesture is associated with a previously identified, known user. If the smart ring  101  causes the external device to perform the comparison, the external device can communicate the results of the comparison to the smart ring  101 . 
     The candidate gesture and the stored authentication gesture do not need to match exactly. The smart ring  101  can determine that the candidate gesture and the stored authentication gesture match if the gestures or the gestural data corresponding to the gestures are similar within a tolerance or suitable threshold. A suitable threshold may be, for example, based at least in part upon the uncertainty of the motion and orientation measurements made by the sensor unit  150 . 
     At block  610 , when the candidate gesture matches the authentication gesture, the smart ring  101  generates a signal indicating that the user has been identified and authenticated as the known user based at least in part upon the first authentication factor. Then, at block  612 , the smart ring  101  transmits the signal to a second device that controls access to a resource. In other embodiments, the smart ring  101  may, in response to the candidate gesture matching the authentication gesture, additionally or alternatively update a record to indicate that the user has been identified and authenticated as the known user associated with the authentication gesture, in a manner similar to block  510 . 
     The signal indicates that the user has been identified and authenticated as a known user. The signal may also indicate why the smart ring  101  determined that the user has been authenticated (e.g., the signal may indicate that the user has been authenticated based at least in part upon matching an authentication gesture to a candidate gesture corresponding to collected gestural data). The signal may also indicate an identity of the known user (e.g., a username or a name of the known user). 
     In some implementations, the smart ring  101  may determine that the known user is a user that is authorized to access the resource. The smart ring  101  may determine whether a user is authorized based at least in part upon information stored in the memory unit  144  indicating what resources can be accessed by known users. The smart ring  101  may also determine whether a user is authorized by communicating with the second device or with another external device such as the server  107 . If the smart ring  101  determines that the known user is authorized to access the resource, then the signal may also indicate that the authenticated user is authorized. 
     Additionally or alternatively, the signal may indicate that the user has been identified and authenticated as a known user based at least in part upon the first authentication factor, but may not indicate whether that known user is authorized to access the resource. In such implementations, the second device, based at least in part upon the signal, determines whether the known user is a user that is authorized to access the resource. 
     In any case, the signal may be generated by the controller  140  or, more specifically, by the processor unit  142 . The signal may be an electromagnetic signal that carries information indicating that the user has been authenticated. The generated signal may be transmitted to the second device by the communication unit  160 . 
     Continuing on to  FIG.  6 B , which illustrates additional steps of example method  600 , at blocks  614 ,  616 , and  618 , the smart ring  101  performs a second authentication operation. It is understood that while the second authentication operation (e.g., blocks  614 ,  616 , and  618 ) is depicted as taking place after the first authentication operation (e.g., blocks  606 ,  608 ,  610 , and  612 ), the order of the first and second authentication operations may be switched. Further, each of the authentication operations may occur simultaneously. For example, the user may perform a gesture that also involves a bump (e.g., contact, discussed in further detail below with respect to block  614 ) of the smart ring  101  with a second device. The smart ring  101  may only perform the second authentication operation if the first authentication operation positively authenticates the user as a known user. Further, the smart ring  101  may only perform the second authentication operation if contact (block  614 ) is detected within a short amount before or after the gestural data are collected (block  606 ) (e.g., less than 10-30 seconds). 
     Beginning at block  614 , the sensor unit  150  detects contact between the smart ring  101  and a component external to the smart ring  101 . The detected contact represents a second authentication factor. The contact that the sensor unit  150  detects may be physical contact between the smart ring  101  and the component, or may be close physical proximity (e.g., on the order of centimeters or on the order of the thickness of the housing  110 ). For example, tactile sensors of the smart ring  101  may detect physical contact or a physical “bump” between the smart ring  101  and the component. As another example, proximity sensors, such as an NFC device, may detect signal(s) transmitted between the smart ring  101  and an NFC circuit of the component, indicating that the smart ring  101  is within NFC-range of the component. 
     The component external to the smart ring  101  may be a component of the second device which controls access to the resource. For instance, the component may be an NFC circuit within the housing of the second device. As an example, the second device may be the secure access panel  432 . The wearer of the smart ring  101  may perform a gesture with the hand wearing the smart ring  101  and then perform a bump between the smart ring  101  and the secure access panel  432 . 
     In other implementations, the component external to the smart ring  101  may be a third device, distinct from and external to the smart ring  101  and the second device. For example, the component may be another ring of the user (e.g., the ring  424 ), another device (e.g., the mobile device  422 , the user device  104 , or the mobile device  106 ), or a hardware token. 
     At block  616 , in response to detecting the contact between the smart ring  101  and the component, the smart ring  101  generates a second signal, and the smart ring  101  transmits the second signal to the second device at block  618 . The signal may be an electromagnetic signal that carries information indicating that the smart ring  101  has made contact with the component. The signal indicates that the particular user has been identified and authenticated as the known user based at least in part upon the second authentication factor. As in blocks  610  and  612 , the controller  140  (or more specifically the processor unit  142 ) may generate the signal at block  616  and the communication unit  160  may transmit the signal. 
     The smart ring  101  may perform steps  616  and  618  in response to the fact that the smart ring  101  has contacted the component. In some implementations, the smart ring  101  may also receive additional information from the component before performing steps  616  and  618 . For instance, during the contact and/or the proximity of the smart ring  101  and the component, the component may communicate an identifier of the component to the smart ring  101 . The smart ring  101  may compare this identifier to stored identifiers on the memory unit  144  of the smart ring  101  or on the memory  109  of the server  107  to determine whether the component is associated with a known user. For example, the identifier may correspond to a component of a vehicle of the known user, or the identifier may correspond to a device or token of the known user. By comparing the identifier to identifiers of devices associated with the known user, the smart ring  101  (possibly in conjunction with the server  107 ) can determine that (a) the second device is associated with the known user, in the case where the component is a component of the second device, or (b) the user is in possession of a component associated with the known user, in the case where the component is a third device. In response to receiving an identifier associated with the known user, the smart ring  101  may then perform steps  616 - 618 . The signal transmitted at  618  may indicate that the received identifier is associated with the known user. 
     In addition, the smart ring  101  may receive a signal from the component indicating that the component has detected contact with the smart ring  101 . The smart ring  101  may perform steps  616  and  618  in response to receiving this signal. In some implementations, the smart ring  101  may only perform steps  616  and  618  if the smart ring  101  receives this signal from the component within a short time period of detecting the contact with the component (e.g., on the order of 10-30 seconds or less). 
     At block  620 , when the second device receives the first and the second signals, the smart ring  101  causes the second device to grant the user access to the resource in response to determining that the first and second signals indicate that the particular user has been authenticated based at least in part upon both the first and second authentication factors. As mentioned previously, the second device may grant access to the resource upon receiving the first and the second signals and determining that the first and second signals indicate that the particular user has been authenticated as a known user, or the second device may need to perform additional processing to determine whether the authenticated user is authorized to access the resource. 
     The resource may be a physical resource or a digital resource. For example, in the case where the second device is the secure access panel  432 , the second device may grant access to a physical space in response to receiving the first and second signals. In other scenarios, the second device may be a computing device, such as the mobile device  422  or the personal computer  444 . In response to receiving the first and the second signals, the computing device may grant the smart ring  101  or the user access to digital information stored on the computing device or accessible through the computing device. Still further, the resource may be control over the second device or a device that the second device manages access to. For instance, the second device may manage access to control over a vehicle, a security system, or a computing device. 
     In the case where the second device is another smart ring  436  worn by another user, the other smart ring  436  may similarly transmit signals to the smart ring  101  indicating that the other wearer is an authenticated user and that the other smart ring  436  has been in contact or proximity with the smart ring  101 . In response to receiving these signals from the other smart ring  436 , the smart ring  101  may grant the smart ring  436  access to an information resource that the smart ring  101  controls access to, such as digital information stored on the smart ring  101  or on a device paired with the smart ring  101  such as the user device  104 , the mobile device  106 , or the server  107 . The smart ring  101  may, based at least in part upon the received signals, determine whether the authenticated user is authorized to access the information resource by, for example, comparing the identity of the authenticated user included in the signal to known users stored on the smart ring  101  or the server  107 . 
     If the smart ring  101  grants access to the smart ring  436 , and the smart ring  436  has similarly granted the smart ring  101  access within a short period of time (e.g., on the order of seconds or minutes), then two rings  101 ,  436  may perform or allow an exchange of information between the two rings  101 ,  436  or devices in communication with the two rings  101 ,  436  and associated with their respective users. Further, the two rings  101 ,  436  may execute an agreement, such as a contract, between the two users. For example, each ring may sign an agreement between the user of the ring and the user of the other ring using an identity of the user of the ring. Such situations may occur, for example, if the two users perform a secret handshake gesture that either includes a bump is or is performed directly before or directly after a bump. Each user may also perform an individual gesture that does not involve the other user&#39;s hand but that is performed either directly before or directly after a bump between the two rings. 
       FIG.  7    illustrates an example method  700  for identifying and authenticating a user using contact data collected by the smart ring  101  indicating a sequence of taps of the smart ring  101  according to one embodiment. In the example method  700 , the smart ring  101  performs an authentication operation using an authentication factor corresponding to a sequence of taps. In some implementations, the method  700  can begin at block  702 . In other implementations, the method  700  may begin at block  706 . 
     At block  702 , sensors of the smart ring  101  (e.g., sensor unit  150 ) detect a sequence of taps of the smart ring  101  during an enrollment mode or set-up mode of the smart ring  101  by collecting contact data. The smart ring  101  may perform block  702  in a manner similar to blocks  602  and  502 . The smart ring  101  may enter an enrollment mode in order to register a new user to utilize the smart ring  101 , or to update a profile of an existing known user of the smart ring  101 . During the enrollment mode, a user may provide an identification to the smart ring  101  besides the contact data indicating the sequence of taps, in order for the smart ring  101  to be associated the detected sequence of taps with a particular identity. For instance, the user may set up a profile on the smart ring  101  itself or by pairing the smart ring  101  with another device, such as the mobile device  422  or the mobile device  106 . The user may provide a username associated with the user and/or some other suitable form of identification such that the smart ring  101  can associate the sequence of taps detected during the enrollment mode to an identified, known user. During the same enrollment mode, the smart ring  101  may collect biometric, gestural, and contact data. 
     While the smart ring  101  is in the enrollment mode, the user can tap the smart ring in a particular sequence that the user wishes to associate with their identity. The smart ring  101  may itself prompt the user to perform the sequence of taps (e.g., via output unit  190 ) or the user device  104  or the mobile device  106  paired with the smart ring  101  may prompt the user. In this way, the smart ring  101  can determine that contact data collected directly after the prompt is to be associated with a specific sequence of taps. The smart ring  101  may prompt the user to perform the sequence of taps several times in order for the smart ring  101  to identify a pattern corresponding to the sequence of taps. 
     A “tap” corresponds to the smart ring  101  detecting contact with a component external to the smart ring  101 . Thus, while the sequence of taps may correspond to a user tapping on the smart ring  101  or a portion of the smart ring  101  (e.g., tapping on the smart ring  101  with a finger of the user), the sequence of taps may correspond with the user tapping the smart ring  101  against any object external to the smart ring  101 , such as a door, computing device, or other smart ring. The contact data indicating the sequence of taps may include, for example, acceleration, vibration, and tactile data indicating a tap of the smart ring with another object. The smart ring  101  may differentiate a deliberate tap from background vibration based at least in part upon the contact data. For example, the smart ring  101  may compare the magnitudes of the detected vibration, acceleration, or force applied to the smart ring  101  to threshold magnitudes comparable to background or accidental contact. 
     Contact that the sensor unit  150  detects as a tap of the sequence of taps may be physical contact between the smart ring  101  and another object. Multiple taps detected within a short time period (e.g., on the order of seconds or fractions of a second) may be determined by the smart ring  101  to belong to the same sequence of taps. 
     At block  704 , the smart ring  101  determines an authentication pattern of the identified user based at least in part upon the sequence of taps detected during the enrollment mode and stores the authentication pattern. The smart ring  101  may determine the authentication pattern using the controller  140 . Additionally or alternatively, the smart ring  101  may communicate all or a portion of the collected contact data to the server  107 , the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 , which may in turn perform the analysis on the contact data to determine the authentication pattern. The authentication pattern corresponds to the pattern of the detected sequence of taps. The analyzing device (whether it is the smart ring  101  or an external device) may determine features of the sequence such as, for example, the rhythm, tempo, frequency, or beat of the taps, or the time between each tap. The collection of sequence features may collectively make up the authentication pattern. 
     In addition to associating the authentication pattern with the identified user, the smart ring  101  may also associate the authentication pattern with unlocking a single resource or with unlocking access to multiple resources. For example, if the smart ring  101  detects proximity to a second device controlling access to a resource while (or shortly before or after) detecting the sequence of taps, the smart ring  101  may associate the authentication pattern with the particular second device. The second device may transmit an identifier of the second device to the smart ring  101  in order for the smart ring  101  to associate the authentication pattern with the second device. The second device may transmit the identifier in response to a request from the smart ring  101 , or in response to detecting proximity of the smart ring  101  or contact with the smart ring  101 . Alternatively or additionally, using the user input unit  170  or a paired device, the user may indicate to the smart ring  101  that the authentication pattern is to be associated with unlocking a particular resource or device. 
     In some implementations, the smart ring  101  may associate the authentication pattern with the smart ring  101  making contact with a particular object. For instance, the smart ring  101  may detect that the sequence of taps has been made against a particular second device controlling access to a resource or against a particular component (e.g., the device or component may transmit an identifier to the smart ring  101 ). 
     In any case, the smart ring  101  associates the authentication pattern with the particular identified user. As an example, the smart ring  101  may collect contact data during the enrollment mode while the user performs taps the smart ring  101  against an object in a unique pattern known only to the user. The smart ring  101  detects the sequence of taps based at least in part upon the contact data. The analyzing device can determine the specific pattern corresponding to the sequence of taps, and classify this specific pattern as an authentication pattern associated with the identified user. This specific pattern can then be stored as an authentication pattern. 
     The analyzing device itself may store the authentication pattern. In some implementations, the analyzing device may communicate the authentication pattern to the smart ring  101 , and the smart ring  101  may store the authentication pattern on the memory unit  144 . Alternatively or in addition, the analyzing device may communicate the authentication pattern to the server  107 , which may function as an authentication server, as mentioned previously. 
     At block  706 , sensors of the smart ring  101  collect, outside the enrollment mode, contact data indicating a sequence of taps between the smart ring  101  and a component external to the smart ring. The smart ring  101  may constantly collect contact data in order to detect when a user deliberately taps the smart ring  101  against an object in a pattern. Alternatively or additionally, the smart ring  101  may collect contact data in response to a request from the user made using the user input unit  170 . For example, the user may indicate to the smart ring  101  that the smart ring  101  should authenticate the user as a known user so that the user may access a particular resource. Still further, the smart ring  101  may collect the contact data in response to receiving a signal from a second device external to the smart ring  101 . The second device controls access to a physical or digital resource. For example, the second device may correspond to the secure access panel  432  controlling access to a physical resource. As another example, the second device may be a device that controls access to digital information, such as the mobile device  422 , the server  442 , the personal computer  444 , or another smart ring  436  or other wearable device worn by another user. When the smart ring  101  is in proximity to the second device, the second device may transmit a signal to the smart ring  101  indicating that the smart ring  101  should authenticate the user of the smart ring  101  in order to access the resource. The smart ring  101  may indicate to the user (e.g., via the output unit  190 ) that the user should perform an authentication pattern in order to authenticate themselves. 
     The sensor unit  150  detects the sequence of taps corresponding to the candidate pattern in a manner analogous to how the sensor unit  150  detects the sequence of taps corresponding to the authentication pattern while the smart ring  101  is in an enrollment mode. The user may cause the smart ring  101  to come into contact with a physical body part of the user (e.g., the user may tap the smart ring  101  with a finger), or with another component external to the smart ring  101  (e.g., the user may tap the smart ring  101  against another object). The component may be a component of the second device which controls access to the resource. For instance, the second device may be the secure access panel  432 . The wearer of the smart ring  101  may perform a sequence of taps with the smart ring  101  against the secure access panel  432 . In other implementations, the component external to the smart ring  101  may be a third device or object, distinct from and external to the smart ring  101  and the second device. For example, the component may be another ring of the user (e.g., the ring  424 ), another device (e.g., the mobile device  422 , the user device  104 , the mobile device  106 , another smart ring  436 ), or a hardware token. The component could also be a non-electronic object, such as a door (e.g., a user could perform a sequence of taps against a door corresponding to a coded or secret knock). 
     The smart ring  101  (or a separate analyzing device, in a manner analogous to block  704 ) can determine that the sequence of taps corresponds to a candidate pattern. At blocks  708  and  710 , the smart ring performs an authentication operation by (i) comparing the candidate pattern to an authentication pattern for a known user to determine whether the candidate pattern matches the authentication pattern (block  708 ), and (ii) when the candidate pattern matches the authentication pattern, authenticating the particular user by updating a record to indicate that the particular user has been identified and authenticated as the known user (block  710 ). 
     More particularly, at block  708 , the smart ring  101  compares the candidate pattern collected and determined at block  706  to an authentication pattern for a known user to determine whether the candidate pattern matches the authentication pattern. If optional steps  702  and  704  have not been performed, the smart ring  101  may compare the candidate pattern to authentication patterns included in a general database of authentication patterns for known individuals stored externally, such as at the server  107 . In implementations where steps  702  and  704  have been performed, then the candidate pattern is compared to the authentication pattern collected while the smart ring  101  was in an enrollment mode. The authentication pattern may be stored at the smart ring  101 , such as in the memory unit  144 , or may be stored on an external device, such as the server  107 , the user device  104 , the mobile device  106 , the personal computer  444 , or the mobile device  422 . In implementations where the authentication pattern is stored at a device external to the smart ring  101 , the smart ring  101  may communicate all or a portion of the collected contact data to the external device to facilitate comparison between the candidate pattern and the authentication pattern. 
     The external device or the smart ring  101  then compares the candidate pattern to the stored authentication pattern. The stored authentication pattern is associated with a previously identified, known user. If the smart ring  101  causes the external device to perform the comparison, the external device can communicate the results of the comparison to the smart ring  101 . 
     The candidate pattern and the stored authentication pattern may not need to match exactly. The smart ring  101  can determine that the candidate pattern and the stored authentication pattern match if the features of the sequences of taps or the contact data corresponding to the sequences of taps are similar within a tolerance or suitable threshold. A suitable threshold may be, for example, based at least in part upon the uncertainty of the contact data measurements made by the sensor unit  150 , or on the precision of the human mind in performing a time-dependent rhythm. 
     At block  710 , when the candidate pattern matches the authentication pattern, the smart ring  101  authenticates the user by updating a record to indicate that the user has been identified and authenticated as the known user associated with the authentication pattern. If the collected candidate pattern matches the authentication pattern, then the smart ring  101  has both (1) identified the particular user as the known user associated with the authentication pattern, and (2) authenticated the particular user to actually be the known user associated with the authentication pattern. 
     The smart ring  101  updates the record by recording in the memory unit  144  an indication of the positive match between the collected candidate gesture and the authentication pattern. The smart ring  101  may update the record in a manner similar to block  510 , for example. The record may correspond to a location in the memory unit  144  that devices external to the smart ring  101  and/or components internal to the smart ring  101 , such as the processor unit  142 , can query to determine whether the user is authenticated. Alternatively or in addition, whenever the controller  140  determines that the record has been updated to reflect than an authentication operation has been performed, the controller  140  can communicate this update to devices and/or components external or internal to the smart ring  101 . 
     The update to the record may indicate why the smart ring  101  determined that the user has been authenticated (e.g., the record may indicate that the candidate pattern matched an authentication pattern), or the update to the record may indicate that the current wearer of the ring is an authenticated user, e.g., that the smart ring  101  is in an authenticated state. If the sensor unit  150  determines that the user has removed the ring  101  from their finger, then the smart ring  101  may update the record to indicate that the smart ring  101  is no longer in an authenticated state. 
     At block  712 , in response to the record indicating that the particular has been identified and authenticated, the smart ring  101  transmits a signal to a second device that controls access to a resource. The signal indicates that the user has been identified and authenticated as a known user. Similar to the update to the record, the signal may indicate why the smart ring  101  determined that the user has been authenticated (e.g., the signal may indicate that the user has been authenticated based at least in part upon matching a candidate pattern to an authentication pattern of a known user). The signal may also indicate an identity of the known user (e.g., a username or a name of the known user) and/or an identifier of the smart ring  101 . It is understood that in other example methods, additional authentication operations may be performed by the smart ring prior to transmitting the signal at block  712 , or prior to receiving access to the resource at block  714 . 
     In some implementations, the smart ring  101  may determine that the known user is a user that is authorized to access the resource. The smart ring  101  may determine whether a user is authorized based at least in part upon information stored in the memory unit  144  indicating what resources can be accessed by known users. The smart ring  101  may also determine whether a user is authorized by communicating with the second device or with another external device such as the server  107 . If the smart ring  101  determines that the known user is authorized to access the resource, then the signal may also indicate that the authenticated user is authorized. Further, the smart ring  101  may only transmit the signal in response to determining that the authenticated user is authorized. 
     Additionally or alternatively, the signal may indicate that the user has been identified and authenticated as a known user based at least in part upon an authentication factor corresponding to an authentication pattern, but may not indicate whether that known user is authorized to access the resource. In such implementations, the second device, based at least in part upon the signal, determines whether the known user is a user that is authorized to access the resource. 
     In any case, the signal may be generated by the controller  140  or, more specifically, by the processor unit  142 . The signal may be an electromagnetic signal that carries information indicating that the user has been authenticated. The generated signal may be transmitted to the second device by the communication unit  160 . 
     In some implementations, the smart ring  101  may also receive additional information from the component that the smart ring  101  has contacted or from the second device controlling access to the resource before updating the record at  710  or transmitting the signal at  712 . For instance, during the sequence of taps is and/or the proximity of the smart ring  101  and the component, the component may communicate an identifier of the component to the smart ring  101 . The authentication pattern may be associated with the identifier (as noted above with respect to block  704 ) such that the pattern must be performed against the particular component in order for the smart ring  101  to authenticate the user based at least in part upon the authentication pattern. 
     As another example, the smart ring  101  may receive an identifier from the second device that controls access to the resource (which may or may not include the component that the smart ring  101  came into contact with) when the smart ring  101  is in proximity of the second device. The authentication pattern may be associated with the second device (as noted above with respect to block  704 ) such that the authentication pattern only serves to authorize the authenticated user to access the resource controlled by the second device. 
     At block  714 , when the second device receives the signal transmitted by the smart ring  101  at block  712 , the smart ring  101  causes the second device to grant the user access to the resource in response to determining that the signal indicates that the particular user has been authenticated. As mentioned previously, the second device may grant access to the resource upon receiving the signal, or the second device may need to perform additional processing to determine whether the authenticated user is authorized to access the resource. 
     As discussed with reference to block  620 , the resource may be a physical resource or a digital resource. For example, in the case where the second device is the secure access panel  432 , the second device may grant access to a physical space in response to receiving the signal. In other scenarios, the second device may be a computing device, such as the mobile device  422  or the personal computer  444 . In response to receiving the signal, the computing device may grant the smart ring  101  or the user access to digital information stored on the computing device or accessible through the computing device. Still further, the resource may be control over the second device or a device that the second device manages access to. For instance, the second device may manage access to control over a vehicle, a security system, or a computing device. The second device may also be another smart ring  436  worn by another user, as discussed with reference to  FIG.  6   . 
     Examples of Other Considerations 
     When implemented in software, any of the applications, services, and engines described herein may be stored in any tangible, non-transitory computer readable memory such as on a magnetic disk, a laser disk, solid state memory device, molecular memory storage device, or other storage medium, in a RAM or ROM of a computer or processor, etc. Although the example systems disclosed herein are disclosed as including, among other components, software or firmware executed on hardware, it should be noted that such systems are merely illustrative and should not be considered as limiting. For example, it is contemplated that any or all of these hardware, software, and firmware components could be embodied exclusively in hardware, exclusively in software, or in any combination of hardware and software. Accordingly, while the example systems described herein are described as being implemented in software executed on a processor of one or more computer devices, persons of ordinary skill in the art will readily appreciate that the examples provided are not the only way to implement such systems. 
     The described functions may be implemented, in whole or in part, by the devices, circuits, or routines of the system  100  shown in  FIG.  1   . Each of the described methods may be embodied by a set of circuits that are permanently or semi-permanently configured (e.g., an ASIC or FPGA) to perform logical functions of the respective method or that are at least temporarily configured (e.g., one or more processors and a set instructions or routines, representing the logical functions, saved to a memory) to perform the logical functions of the respective method. 
     While the present disclosure has been described with reference to specific examples, which are intended to be illustrative only and not to be limiting of the present disclosure, it will be apparent to those of ordinary skill in the art that changes, additions or deletions may be made to the disclosed embodiments without departing from the spirit and scope of the present disclosure. 
     Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently in certain embodiments. 
     As used herein, any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification may not be all referring to the same embodiment. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements may not be limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive “or” and not to an exclusive “or.” For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. Generally speaking, when a system or technique is described as including “a” part or “a” step, the system or technique should be read to include one or at least one part or step. Said another way, for example, a system described as including a blue widget may include multiple blue widgets in some implementations (unless the description makes clear that the system includes only one blue widget). 
     Throughout this specification, some of the following terms and phrases are used. 
     Communication Interface according to some embodiments: Some of the described devices or systems include a “communication interface” (sometimes referred to as a “network interface”). A communication interface enables the system to send information to other systems and to receive information from other systems, and may include circuitry for wired or wireless communication. 
     Each described communication interface or communications unit (e.g., communications unit  160 ) may enable the device of which it is a part to connect to components or to other computing systems or servers via any suitable network, such as a personal area network (PAN), a local area network (LAN), or a wide area network (WAN). In particular, the communication unit  160  may include circuitry for wirelessly connecting the smart ring  101  to the user device  104  or the network  105  in accordance with protocols and standards for NFC (operating in the 13.56 MHz band), RFID (operating in frequency bands of 125-134 kHz, 13.56 MHz, or 856 MHz to 960 MHz), Bluetooth (operating in a band of 2.4 to 2.485 GHz), Wi-Fi Direct (operating in a band of 2.4 GHz or 5 GHz), or any other suitable communications protocol or standard that enables wireless communication. 
     Communication Link according to some embodiments. A “communication link” or “link” is a pathway or medium connecting two or more nodes. A link between two end-nodes may include one or more sublinks coupled together via one or more intermediary nodes. A link may be a physical link or a logical link. A physical link is the interface or medium(s) over which information is transferred, and may be wired or wireless in nature. Examples of physicals links may include a cable with a conductor for transmission of electrical energy, a fiber optic connection for transmission of light, or a wireless electromagnetic signal that carries information via changes made to one or more properties of an electromagnetic wave(s). 
     A logical link between two or more nodes represents an abstraction of the underlying physical links or intermediary nodes connecting the two or more nodes. For example, two or more nodes may be logically coupled via a logical link. The logical link may be established via any combination of physical links and intermediary nodes (e.g., routers, switches, or other networking equipment). 
     A link is sometimes referred to as a “communication channel.” In a wireless communication system, the term “communication channel” (or just “channel”) generally refers to a particular frequency or frequency band. A carrier signal (or carrier wave) may be transmitted at the particular frequency or within the particular frequency band of the channel. In some instances, multiple signals may be transmitted over a single band/channel. For example, signals may sometimes be simultaneously transmitted over a single band/channel via different sub-bands or sub-channels. As another example, signals may sometimes be transmitted via the same band by allocating time slots over which respective transmitters and receivers use the band in question. 
     Memory and Computer-Readable Media according to some embodiments. Generally speaking, as used herein the phrase “memory” or “memory device” refers to a system or device (e.g., the memory unit  144 ) including computer-readable media (“CRM”). “CRM” refers to a medium or media accessible by the relevant computing system for placing, keeping, or retrieving information (e.g., data, computer-readable instructions, program modules, applications, routines, etc.). Note, “CRM” refers to media that is non-transitory in nature, and does not refer to disembodied transitory signals, such as radio waves. 
     The CRM may be implemented in any technology, device, or group of devices included in the relevant computing system or in communication with the relevant computing system. The CRM may include volatile or nonvolatile media, and removable or non-removable media. The CRM may include, but is not limited to, RAM, ROM, EEPROM, flash memory, or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store information, and which can be accessed by the computing system. The CRM may be communicatively coupled to a system bus, enabling communication between the CRM and other systems or components coupled to the system bus. In some implementations the CRM may be coupled to the system bus via a memory interface (e.g., a memory controller). A memory interface is circuitry that manages the flow of data between the CRM and the system bus. 
     Network according to some embodiments. As used herein and unless otherwise specified, when used in the context of system(s) or device(s) that communicate information or data, the term “network” (e.g., the networks  105  and  440 ) refers to a collection of nodes (e.g., devices or systems capable of sending, receiving or forwarding information) and links which are connected to enable telecommunication between the nodes. 
     Each of the described networks may include dedicated routers responsible for directing traffic between nodes, and, optionally, dedicated devices responsible for configuring and managing the network. Some or all of the nodes may be also adapted to function as routers in order to direct traffic sent between other network devices. Network devices may be inter-connected in a wired or wireless manner, and network devices may have different routing and transfer capabilities. For example, dedicated routers may be capable of high volume transmissions while some nodes may be capable of sending and receiving relatively little traffic over the same period of time. Additionally, the connections between nodes on a network may have different throughput capabilities and different attenuation characteristics. A fiberoptic cable, for example, may be capable of providing a bandwidth several orders of magnitude higher than a wireless link because of the difference in the inherent physical limitations of the medium. If desired, each described network may include networks or sub-networks, such as a local area network (LAN) or a wide area network (WAN). 
     Node according to some embodiments. Generally speaking, the term “node” refers to a connection point, redistribution point, or a communication endpoint. A node may be any device or system (e.g., a computer system) capable of sending, receiving or forwarding information. For example, end-devices or end-systems that originate or ultimately receive a message are nodes. Intermediary devices that receive and forward the message (e.g., between two end-devices) are also generally considered to be “nodes.” 
     Processor according to some embodiments. The various operations of example methods described herein may be performed, at least partially, by one or more processors (e.g., the one or more processors in the processor unit  142 ). Generally speaking, the terms “processor” and “microprocessor” are used interchangeably, each referring to a computer processor configured to fetch and execute instructions stored to memory. By executing these instructions, the processor(s) can carry out various operations or functions defined by the instructions. The processor(s) may be temporarily configured (e.g., by instructions or software) or permanently configured to perform the relevant operations or functions (e.g., a processor for an Application Specific Integrated Circuit, or ASIC), depending on the particular embodiment. A processor may be part of a chipset, which may also include, for example, a memory controller or an I/O controller. A chipset is a collection of electronic components in an integrated circuit that is typically configured to provide  1 /O and memory management functions as well as a plurality of general purpose or special purpose registers, timers, etc. Generally speaking, one or more of the described processors may be communicatively coupled to other components (such as memory devices and I/O devices) via a system bus. 
     The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the processor or processors may be located in a single location (e.g., within a home environment, an office environment or as a server farm), while in other embodiments the processors may be distributed across a number of locations. 
     Words such as “processing,” “computing,” “calculating,” “determining,” “presenting,” “displaying,” or the like may refer to actions or processes of a machine (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or a combination thereof), registers, or other machine components that receive, store, transmit, or display information. 
     Although specific embodiments of the present disclosure have been described, it will be understood by those of skill in the art that there are other embodiments that are equivalent to the described embodiments. Accordingly, it is to be understood that the present disclosure is not to be limited by the specific illustrated embodiments.