Patent Publication Number: US-9904814-B2

Title: Secure element

Description:
BACKGROUND 
     Near-field communications (NFC) technology may be used in secure transactions such as contactless payment and loyalty card or coupon use. An NFC contactless payment chipset may include an NFC controller, an NFC antenna, and a secure element (SE). The SE may provide transaction security by providing a secure memory to secure store applications or credentials, such as account numbers or encryption information, or provide a secure execution space for secure execution of transaction-related applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain examples are described in the following detailed description and in reference to the drawings, in which: 
         FIG. 1A  illustrates an underside view of an example system and  FIG. 1B  illustrates a side view of the example system along the axis A of  FIG. 1A ; 
         FIG. 2A  illustrates an underside view of an example system and  FIG. 2B  illustrates a side view of the example system along the axis A of  FIG. 2A ; 
         FIG. 3  illustrates an example point-of-sale (POS) terminal having an NFC controller and an SE mounted on the NFC controller; 
         FIG. 4  illustrates an example POS terminal including a heat spreader and a processor; and 
         FIG. 5  illustrates an example mobile device including NFC controller having an SE coupled to an underside of the NFC controller. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EXAMPLES 
     Point of sale (POS) terminals handle sensitive cardholder information. Various attempts to secure cardholder information have been implemented. For example, the Payment Card Industry Data Security Standard (PCI DSS) has been promulgated by the PCI Security Standards Counsel to increase controls around cardholder data. 
     PCI DSS compliance may require expensive hardware and manufacturing techniques. For example, certain components, such as the SE, may be required to be housed inside a hardened chassis that is protected from intrusion. Accordingly, POS terminal manufacture may require use of hardened facilities specializing in producing security hardened components. Additionally, POS terminals may require expensive certification procedures. Mobile POS (MPOS) terminals may be implemented using mobile devices such as tablets, smartphones, notebooks, or other PCs. Assembly of the entire mobile device in a hardened facility may be prohibitively expensive. 
     Aspects of the disclosed technology provide a single package combining an SE and a bus interface chip. The bus interface chip provides a secure interface for the SE to a system bus. For example, the bus interface chip may be an NFC controller. The combined package may be manufactured in a secure manner that can later be integrated into a POS terminal with requiring secure manufacturing or an intrusion protected enclosure. In some examples, the SE is inverted and mounted to the underside of the NFC controller. In these examples, when the NFC controller is mounted on a printed circuit board (PCB) it prevents access to the SE, protecting the SE against various attack vectors. 
       FIG. 1  illustrates an example system  100  having a bus interface chip  101  and an SE  105  coupled to the underside of the bus interface chip  101 .  FIG. 1A  illustrates an underside view of the system  100  and  FIG. 1B  illustrates a side view of the system  100  along the axis A of  FIG. 1A . In some cases, the illustrated system  100  may be installable on a PCB to be used in a MPOS or a smart card. In some implementations, the illustrated system  100  may be manufactured in a secure facility and then integrated into a mobile device such as a smart phone or tablet in another facility. In other implementations, the illustrated system  100  may be integrated into a smart card to be used by a cardholder. For example, the system  100  may be manufactured to meet PCI DSS compliance requirements such that later integration into a further device does not require PCI DSS compliance. 
     The example system  100  may include a bus interface integrated circuit (IC)  101 . The bus interface IC may provide an interface to a system bus for the SE  105 . In these examples, the SE  105  may not have a direct connection to the system bus. Instead, communications with the SE  105  may pass through the bus interface IC  101 . For example, when the system  100  is installed in a device, the bus interface IC  101  may provide an interface for the SE  105  to the device&#39;s Peripheral Component Interconnect (PCI) bus. In some implementations, the bus interface IC  101  may serve other functions. For example, the bus interface IC  101  may be an NFC controller, a Bluetooth or Wi-Fi controller, or a storage controller. 
     A potential attack on an SE may be a thermal probe attack. In a thermal probe attack, an attacker may try to correlate temperature fluctuations in the chip with chip operations to determine internal operations or data. In some cases, the bus interface IC  101  may perform functions during transactions in which the SE  105  is active. The heat created by the bus interface IC  101  may introduce noise, creating ambiguous readings to a thermal probe attack. For example, in a contactless payment situation, the NFC controller may be active whenever the SE  105  is active. Accordingly, the NFC controller may serve as a suitable bus interface IC  101 . 
     The bus interface IC  101  may have an underside  102 . The underside  102  may be the side of the IC  101  that faces the PCB when installed. The IC  101  may also have an upper side  109  that faces away from the PCB when installed and houses the IC&#39;s  101  active components. The underside  102  may include a first plurality of internal contacts  104  and a plurality of external contacts  103 . For example, the plurality of internal contacts  104  may be traces on the underside of the IC  101  and the plurality of external contacts  103  may be pins extending from the underside of the IC  101  to clear the height of the SE  105 . In some implementations, the external contacts  103  may be coupled to solder bumps  108  forming a BGA  110  that surrounds the SE  105 . 
     The system  100  may also include an SE IC  105 . The SE  105  may be mounted on the underside of the bus interface IC  101 . The SE  105  may include a second plurality of internal contacts  106 . For example, the second plurality of internal contacts  106  may electrical traces corresponding to the internal contacts  104  of the bus interface IC  101 . The two sets of internal contacts  104  may be coupled, for example by solder connections. For example, the SE  105  may be mounted to the bus interface IC  101  using a solder ball grid array (BGA). In some implementations, the SE  105  lacks any external contacts. Instead, when installed, all power and communication is provided via the bus interface IC  101 . Additionally, in some examples, during operation, communications between the SE  105  and the bus interface IC  101  may use session based encryption, where data flowing over connections  107  is encrypted with time limited session keys. 
     In some implementations, the SE  105  may be mounted on the underside of the bus interface IC  101  such that the plurality of external contacts  103  surrounds the SE  105 . The plurality of external contacts  103  may be arranged a nested arrangement surrounding the SE  105 . For example, the contacts  103  may be arranged in a plurality of nested arrays or grids  111 ,  112 , with each array  111 ,  112  surrounding the SE  105 . This arrangement creates a plurality of rows and columns surrounding the SE  105 . In these implementations, the plurality of external contacts  103  may prevent access to the internal connections  107  when the system  100  is installed. For example, this may impede attack vectors such as power probe or fault injection attacks. Additionally, power probe or fault injection attacks on the external contacts  103  may provide ambiguous results due to the independent operations of the bus interface IC  105 , such as NFC control operations. 
       FIG. 2  illustrates an example system  200  having a bus interface IC  201  with a heat spreader  214  and a SE IC  205  in a package  213  encapsulating the devices.  FIG. 2A  illustrates an underside view of the system  200  and  FIG. 2B  illustrates a side view of the system  200  along the axis A of  FIG. 2A . Similar to the system of  FIG. 1 , the system  200  may installable on a PCB to be used in an MPOS or a smart card. For example, the illustrated system  200  may be manufactured in a secure facility and then integrated into a mobile device such as a smart phone or tablet in another facility. As another example, the illustrated system  200  may be integrated into a smart card to be used by a cardholder. 
     The bus interface IC  201  and the SE  205  may be implemented as described with respect to bus interface IC  101  and the SE  105 , respectively. For example, the SE  205  may be mounted on the underside  202  of the bus interface IC  201  by connections  207  connecting a first plurality of internal contacts  204  of the IC  201  and a second plurality of internal contacts  206  of the SE  205 . In some cases, a plurality of IC  201  external contacts  203  may surround the SE  205  in a nested arrangement  212 . For example, nested tiers  210 ,  211  of solder bumps  208  may form a BGA surrounding the SE  205 . 
     The example system  200  may further include a heat spreader  214 . The heat spreader  214  may be coupled to the bus interface IC  201 . For example, the heat spreader  214  may be coupled to the bus interface IC  201  on the side  209  of the interface IC  201  opposite the underside  202 . The heat spreader  214  may spread heat created by the IC  201  and heat created by the SE  205 . This may further impede thermal probe attacks. In some examples, the heat spreader  214  may be a thermally conductive compound, such as a layer of thermally conductive metal or ceramic. For example, a layer of a commercial thermal interface material (TIM) may be used as the heat spreader  214 . 
     The example system  200  may further include a package  213  encapsulating the bus interface IC  201  and SE IC  205 . In some cases, the package  213  may encapsulate the first and second pluralities of internal contacts  204 ,  206 . In some implementations, the package  213  may be a semiconductor package housing the devices  201 ,  205 . For example, package  213  may be a molded epoxy plastic or ceramic package. In other implementations, the package  213  may be an epoxy or other sealant that secures or hardens the devices against certain attack vectors. In some implementations, the package  213  may incorporate intrusion detection features. Such intrusion detection features allow attacks to be detected and countermeasures performed. For example, if an intrusion is detected, the SE&#39;s  205  data may be deleted. In some cases, a power source in the IC  201  or SE  205  may be connected to the package  213  allowing the chip to detect if the package is broken or removed. For example, the package  213  may include fusible links that are bridged if the package is broken. 
       FIG. 3  illustrates an example POS terminal  300  having an NFC controller  303  and an SE  307  mounted on the NFC controller  303 . In some implementations, the POS terminal  300  may be integrated into a mobile device such as a tablet, smart phone, or laptop computer. In other implementations, the POS terminal  300  may be a peripheral or an independent device. 
     The POS terminal  300  may include a PCB  301 . The PCB  301  may include an array of electrical contacts  302 . For example, the array of electrical contacts  302  may be signal traces arranged to accommodate a BGA for mounting the NFC controller  303 . For example, the array of electrical contacts  302  may be arranged as described with respect to nested arrangements  112  and  212  of  FIGS. 1 and 2 , respectively. 
     The POS terminal  300  may further include an NFC controller  303 . The NFC controller  303  may control near-field communications for the POS terminal  300 . For example, the NFC controller  303  may use a near-field antenna to communicate with a corresponding NFC controller of a cardholder to exchange information conduct a financial transaction. For example, the NFC controller  303  may allow the POS terminal  300  to conduct payment transactions, loyalty card transactions, or coupon transactions. 
     The example NFC controller  303  includes an underside  304  facing the PCB  301 . The underside  304  may include an array of external contacts  305  coupled to the electrical contacts  302  of the PCB  301 . For example, the electrical contacts  305  may be contacts coupled to the electrical contacts  302  by soldering a BGA. 
     The underside  304  may further include a first array of internal contacts  306 . For example, the first array of internal contacts  306  may be electrical traces on the underside  304  of the NFC controller  303  to allow the SE  307  to be mounted to the underside  304 . 
     The POS terminal  300  may further include an SE  307 . The SE  307  may include a second array of internal contacts  308 . The second array of internal contacts  308  may be coupled to the first array of internal contacts  306 . For example, the contacts  306 ,  308  may be coupled by solder connections. 
     In some implementations, the NFC controller  303  may provide an interface to the SE  307 . For example, the NFC controller  303  may provide power and round to the SE  307  via contacts  306 ,  308 . Additionally, the NFC controller  303  may serve as a bus interface for the SE  307  as described above. 
       FIG. 4  illustrates an example POS terminal  400  including a heat spreader  411  and a processor  410 . In some implementations, the POS terminal  400  may be integrated into a mobile device such as a tablet, smart phone, or laptop computer. In other implementations, the POS terminal  400  may be a peripheral or an independent device. 
     Similarly to the example POS terminal  300 , the POS terminal  400  may include a PCB  401  including an array of electrical contacts  405 . The electrical contacts  405  may be arranged as described with respect to nested arrangements  112  and  212  of  FIGS. 1 and 2 , respectively. 
     The POS terminal  400  may include an NFC controller  401  mounted to the PCB  402 . For example, the NFC controller  401  may be mounted on the PCB  402  using a plurality of solder connections  405  coupled to an array of external contacts  409 . The NFC controller  401  may further include a first array of internal contacts  403 . In some implementations, the NFC controller  401  may include a heat spreader  412 . For example, the heat spreader  412  may be implemented as described with respect to heat spreader  214  of  FIG. 2 . 
     The POS terminal  400  may further include an SE  406  mounted to the underside of the NFC controller  401 . For example, the SE  406  may include a second array of internal contacts  407  coupled to the first array of internal contacts  403 . As described with respect to  FIG. 3 , the NFC controller  401  may provide an interface to the SE  406 . For example, all electrical connections, such as ground, power, and communications, of the SE  406  may be provided through the external contacts  409  to the NFC controller  401 . The NFC controller  401  may pass the communications and provide ground and power to the SE  406  via the internal contacts  403 ,  407 . 
     The POS terminal  400  may further include a package  408 . The package  408  may encapsulate the NFC controller  401  and the SE  406 . In some implementations, the package  408  may encapsulate the first and second arrays of internal contacts  403 ,  407 . In some implementations, the package  804  may be as described with respect to the package  213  of  FIG. 2 . 
     The POS terminal  400  may further include a treat spreader  411  mounted on the PCB  402  opposite the NFC controller  401 . For example, the NFC controller  401  defines an upper side of the PCB  402  the heat spreader  411  may be mounted on the underside of the PCB  402  under the SE  406 . The heat spreader  411  may impede thermal probe attacks conducted on the underside of the PCB  402  by distributing and mixing the heat caused by the NFC controller  401  and the SE  406 . The heat spreader  411  may be composed of materials similar to that of heat spreaders  412  and  214 . Alternatively, the heat spreader  411  may be composed of other materials that are unsuitable for mounting directly on chips. 
     The POS terminal  400  may further include a processor  410 . For example, the processor  410  may execute software to allow the POS  400  to conduct transactions, such as financial transactions using the NFC controller  401 . The processor  410  may be coupled to the NFC controller  401  to communicate with the SE  406  via the NFC controller  401 . For example, the processor  410  and the NFC controller  401  may be coupled to a system bus, such as PCI bus. In some implementations, the processor  410  may address communications for the SE  406  to the NFC controller  401 . In other implementations, the SE  406  may appear on the system bus, and the processor  410  may address communication for the SE  406  to the SE  406 . Those communications may be intercepted by the NFC controller  401  and provided to the SE  406  in a secure manner. In some cases, the processor  410  may be mounted on the PCB  402 . In other cases, the processor  410  may be connected to the PCB  402  using connectors and interconnects. 
       FIG. 5  illustrates an example mobile device  500  including an NFC controller  503  having an SE  502  coupled to an underside of the NFC controller  503 . In some implementations, the example mobile device  500  may be able to act as a mobile POS as described above. For example, the mobile device  500  may be an implementation of an example POS of  FIG. 3  or  FIG. 4 . 
     The mobile device  500  may include an NFC controller  501  and an SE  503 . The NFC controller  501  and SE  503  may be as described with respect to NFC controller  303  and SE  307  or  401  and  406  of  FIG. 3 or 4 , respectively. For example, the SE  503  may be coupled to an underside of the NFC controller  501  and surrounded by external electrical contacts of the NFC controller  501 . In some implementations, the NFC  501  may be coupled to a heat spreader, such as heat spreader  412  of  FIG. 4 . 
     The mobile device  500  may further include an NFC antenna  502 . The NFC antenna  502  may allow the NFC controller  501  to send and receive near-field communications. For example, the NFC antenna  502  may allow the NFC controller  501  to pair with an NFC sub-system on a cardholder&#39;s device to conduct a financial transaction. 
     Additionally, in some implementations, the NFC  501  may be coupled to a PCB  508 . For example, the PCB  508  may be as described with respect to PCB  402  of  FIG. 4 . In these implementations, the PCB  508  may have a heat spreader coupled to the PCB opposite the NFC controller, such as heat spreader  411  of  FIG. 4 . 
     The mobile device  500  may further include a processor  504 . For example, the processor may be as described with respect to processor  410  of  FIG. 4  and may communicate with the SE  503  via the NFC controller  501 . For example, the NFC controller  501  may serve as a bus interface for the SE  503  to allow the processor  504  and SE  503  to communicate on a system bus. 
     Additionally, the mobile device  500  may include other components, such as a memory  506  and input/output (I/O) components  505 . The memory  506  may include non-transitory computer readable media such as random-access memory, flash memory, or storage. The I/O  505  may include keyboards, screens, touch screens, wireless or wired network transceivers, or other communication devices. For example, the memory  506  may store computer executable instructions to cause the processor  504  to use the NFC controller  501  to conduct a transaction, such as a financial transaction. For example, the instructions may cause the processor  504  to use the SE  503  for secure data storage or secure program execution. The processor  504  may transmit transaction-related instructions addressed to the SE  503  on a system bus. These communications may be intercepted and relayed to the SE  503  by the NFC controller  501  in a transparent manner. Alternatively, the processor  504  may transmit transaction-related instructions for the SE  503  to the NFC controller  501 . In these cases, the NFC controller  501  may serve as a hub for the SE  503 . 
     In the foregoing description, numerous details are set forth to provide an understanding of the subject disclosed herein. However, implementations may be practiced without some or all of these details. Other implementations may include modifications and variations from the details discussed above. It is intended that the appended claims cover such modifications and variations.