Patent Description:
<CIT> discloses a password generation technique, with a password comprising multiple characters including the user password, variable characters and terminator characters. <CIT> discloses a process in which the number of entered characters is greater than the number of characters in a password. <CIT> discloses an authentication technique. <CIT> discloses an authentication system utilizing a partial password.

In one aspect there is provided a method for authentication according to claim <NUM>. In another aspect there is provided a device for authentication according to claim <NUM>.

<FIG> illustrates an example authentication environment <NUM> in which a user of a user device <NUM> may authenticate to access a secured access-controlled resource <NUM> according to some examples of the present disclosure. As shown in <FIG>, the secured access-controlled resource <NUM> may be a secured access-controlled resource <NUM> of the user device <NUM> or a secured access-controlled resource <NUM> that is provided by a remote device <NUM> that is accessible over a network <NUM>. Secured access-controlled resource <NUM> may include access to one or more files, portions of files (e.g., fields or data structures), applications, access to an operating system, access to the user device <NUM> itself, access to one or more network-based services (e.g., social networking services, file sharing services, email, communications services, and the like), access to a physical object (e.g., through the unlocking of the object by computer control), or the like.

Network <NUM> may include any computing network, including a local area network (LAN), wide area network (WAN), the Internet, or the like. At the user device <NUM>, the user makes an authenticate attempt on requesting access to the secured access-controlled resource <NUM>. An authentication attempt is an attempt by a user to demonstrate possession of valid credentials to access the secured access-controlled resource. As part of the authentication attempt, the client <NUM> may cause a user interface (UI) <NUM> (which may be a graphical UI (GUI)) to be displayed which requests credentials of the user that are required to access the secured access-controlled resource <NUM>. Example credentials include a username, a password, a biometric, a token, a digital certificate, an encryption key, or the like.

The client <NUM> may then pass the credentials entered by the user to the authenticator <NUM>. The authenticator <NUM> may determine whether the credentials entered by the user are valid. If they are valid, the authenticator <NUM> may grant access to the secured access-controlled resource <NUM>. If the credentials are not valid, the authenticator <NUM> may deny access to the secured access-controlled resource <NUM>. If the secured access-controlled resource <NUM> is controlled by the remote device <NUM>, the authenticator <NUM> may send a message across network <NUM> to indicate to the remote device <NUM> whether the user is authorized to access the secured access-controlled resource. Client <NUM> may then inform the user via UI <NUM> whether access was granted or not.

<FIG> illustrates an example authentication environment <NUM> in which a user utilizing a user device <NUM> may authenticate to access a secured access-controlled resource <NUM> according to some examples of the present disclosure. <FIG> is similar to <FIG>, except the authenticator <NUM> is located on a remote device <NUM>. A user enters the credentials via the UI <NUM> of client <NUM> as in <FIG>. In some examples, the UI may be provided entirely by the client <NUM>, but in other examples, the UI may be provided partially by the remote device <NUM> (e.g., via one or more files that are transmitted by the remote device <NUM> and rendered by the client <NUM> to create the UI <NUM>). The client transmits the credentials via the network <NUM> to authenticator <NUM> of remote device <NUM>. The credentials may be encrypted when transmitted across network <NUM>, for example, by utilizing Secure Socket Layer connections.

In the example of <FIG>, the secured access-controlled resource <NUM> may reside at user device <NUM>, remote device <NUM>, or second remote device <NUM>. Authenticator <NUM> may send an indication to the device on which the secured access-controlled resource <NUM> is located to indicate whether the user is authenticated or not - either directly, or through the client <NUM>. In some examples, the indication may be a direct message to the device (e.g., such as user device <NUM> or second remote device <NUM>). In other examples, the authenticator <NUM> may issue a token to client <NUM> if the user successfully authenticates. This token may be sent by the user device <NUM> to whatever device the secured access-controlled resource <NUM> is on. The device (e.g., <NUM>, <NUM>, or <NUM>) then verifies the token and grants the user access to the secured access-controlled resource if the token is verified.

In traditional authentication systems, users type in a credential that is checked against a stored credential (or otherwise verified) to determine if the entered credential is an exact match to the stored credential. While requiring an exact match is, in traditional authentication systems, the most secure verification method to prevent against hackers that are trying to guess the credential by using brute-force attacks, requiring an exact match may be problematic for remote authentication as noise may be introduced by the communication channel which may cause a failed authentication. Further, exact match systems present security vulnerabilities as they expose the exact credential of the user to eavesdroppers. For example, security vulnerabilities may result from nefarious users that eavesdrop on a legitimate user's keyboard as they type in their password (so-called shoulder surfers), use keyloggers that directly steal data from a user's keyboard, or use man-in-the middle attacks that intercept communications such as credentials that may be sent to servers. In systems requiring an exact match for the user's credentials, an eavesdropper need only intercept a single authentication attempt to compromise a user's account.

To better secure against these eavesdropping attacks, some exact match authentication systems require entry of one or more noise symbols interspersed with legitimate credential symbols. Noise symbols are one or more symbols that are not part of the user's credential and are not checked against the stored credential to determine whether there is a match with the user's stored credential. A symbol is one or more data units, such as a character, a byte, a word, or the like. The device that authenticates the password removes these noise symbols to check for an exact match with the stored credential. These techniques may defeat shoulder surfers that attempt to spy a user's password by watching the characters the user types. In addition, certain keyloggers that monitor keys typed by a user or man-in-the middle attackers that intercept a user's communications may also be prevented from determining the user's password by the addition of noise characters in the password as it may take multiple observations to discern the user's real password.

Authenticators in authentication systems that introduce noise symbols in the credential typically need to filter out the noise symbols in the credential before checking for an exact match. To accomplish this, the authenticator must know which symbols are noise symbols and which are part of the credential. In some examples, authentication systems introduce noise symbols at positions of the credential that are specified for all authentication attempts. For example, the authentication system may specify that all authentication attempts must put noise symbols at the beginning, at the end, at both the beginning and end, or at other predetermined positions within the credential symbols. These positions do not change during a subsequent login attempt. That is, each login attempt utilizes extra noise symbols at one or one or more of these same positions.

In other examples, the authenticator (either on the user device or at a remote device) may specify, for a specific authentication attempt, that a user is to place noise symbols in specified positions of the credential. For example, the user may be instructed to insert three noise symbols N before the first, between the second and third, and between the fourth fifth symbols of a password P to produce submitted symbols of {N<NUM>, P<NUM>, P<NUM>, N<NUM>, P<NUM>, P<NUM>, N<NUM>, P<NUM>. Pm} where m is the length of the password P. The symbols used for these noise symbols N may be specified by the authenticator or may be left to the user to decide when they type in the random characters. In some examples, the symbols may be characters and the credential may be a password, thus a user may insert noise characters within a password at specified character positions within the password.

The authenticator then strips out the noise symbols N from the submitted symbols. Authentication is easy to implement on these systems as exact knowledge of where the noise symbols are enables easy removal of those symbols and thus a direct comparison between the entered symbols and the stored credential is possible. These systems may not effectively solve the problems of eavesdropping of passwords because an eavesdropper may also be able to determine where in the password the noise is inserted and thus may be able to accurately remove the noise. For example, if the positions are displayed to a user, a shoulder-surfer would also be able to see which positions are noise symbols. In addition, if the authenticator is located remotely, the authenticator may send a message to the client device indicating where the user should insert noise. This message may be intercepted by a man-in-the middle attack. The potential ways in which attackers can access the specified positions make these systems less effective.

Disclosed in some examples are methods, systems and machine-readable mediums which allow for more secure authentication attempts by implementing authentication systems with credentials that include interspersed noise symbols. These systems which allow noise symbols N in positions determined by the user that are not specified to the authenticator for an authentication attempt produce higher amounts of security from eavesdroppers as there is no way for an eavesdropper to determine in advance where the noise symbols (e.g., characters) are. While these systems are more secure, they are not easy to authenticate. For example, since the position of the noise symbols is not known by the authenticator, it is not easy to ignore the noise symbols N to determine if the remaining characters match the password.

In the disclosed examples, the noise symbols (e.g., characters) and their positions within the credential are not specified for the particular authentication attempt by the system. The user may decide at the time of credential entry where to put the random noise symbols and what the random noise symbols are. The authenticator compares the submitted characters (the credential with the interspersed noise symbols) with the stored credential without knowledge of where the noise symbols are within the credential symbols and without knowledge of what symbols the noise symbols are.

To authenticate the user, the authenticator decomposes the submitted symbols into a plurality of vectors of length m that corresponds to the number of symbols in the valid credentials (e.g., a length of the password). An ordering of the symbols is maintained in each of the plurality of vectors such that the order of each symbol in the vector relative to the other symbol in the vector matches the ordering as received. A distance metric is then calculated that quantifies a distance between each vector and a vector comprising the symbols of the credential. Based on the distance metric, a determination may be made if the credential is matched and the user authenticated. In some examples, the credential is a password, and the symbols are characters.

The present disclosure thus solves a technical problem of providing secure access to access-controlled resources using one or more secure credentials (such as a password) that is resistant to keyloggers, eavesdroppers, and man-in-the middle attacks. This is accomplished through the introduction of user-specified noise symbols (e.g., characters) that are introduced at user-specified locations. The authenticator is not aware of where the noise symbols are introduced or what the noise symbols are. The authenticator decomposes the submitted symbols into a plurality of vectors and utilizes a distance metric to determine if authentication should be granted. In some examples, this method may secure against brute force attacks by limiting the number of authentication attempts a user can make by locking the user out of their account (permanently or temporarily) after a threshold number of unsuccessful login attempts.

<FIG> illustrates a diagram of a data flow <NUM> of an authentication with additional, unspecified noise symbols according to some examples of the present disclosure. According to the example data flow <NUM>, the entered credential <NUM> (e.g., password) may comprise three symbols <NUM>, <NUM>, and <NUM> {P1, P2, P3} in that order, that may be in the form of a character. The user, when entering the credential adds one or more noise symbols <NUM> in the form of noise characters to the credential. In the example shown in <FIG>, for ease of description, only one noise symbol <NUM> is added. The submitted symbols <NUM> that are submitted by the user for authentication, includes the credential symbols <NUM>, <NUM>, and <NUM> (in order) along with the one or more noise symbols <NUM> inserted into the credential symbols.

The authenticator <NUM> includes a vector creator <NUM> that receives the submitted symbols <NUM> and creates a plurality of vectors of length m, where m is a number of symbols of the stored credential <NUM> (e.g., password) of the user (e.g., a length of the valid password). The vectors reflect each of the possible in-order, length m combinations of the submitted symbols <NUM>. The order of the characters in each of the vectors is a same order as an order of the symbols in the submitted symbols <NUM>. That is, if the combined sequence is "plas", and the credential is "pas" then the vectors would all be of length three and would reflect all the possible in-order (i.e., each character maintains the order it appeared in from the submitted symbols <NUM>) combinations. In this example, the vectors would be:
<p, <NUM>, a>, <p, a, s>, <p, <NUM>, s>, <<NUM>, a, s>.

Each vector is then passed to a distance metric calculator <NUM> that calculates a distance between each of the vectors and a vector of the stored credential <NUM>. In some examples, the distance metric may be a Levenshtein distance. In other examples, a distance metric may compare each symbol of each vector to the corresponding position in the stored credential <NUM>. If the symbols match, then the score may not be incremented. If the symbols do not match, the score may be incremented. In other examples, a higher score reflects a better match and thus symbols that match may cause the score to be incremented and symbols that do not match may cause no change in the score or may cause the score to be decremented. In still other examples, the distance metric may be a correlation to the stored credential <NUM>, such as a Pearson correlation coefficient. In other examples, other edit distance metrics or algorithms may be used.

The distance metrics for each of the vectors is then passed to the match determination logic <NUM>. In some examples, the match determination logic <NUM> identifies the distance metric that signifies a closest match with the stored credential <NUM> (e.g., a smallest distance). This may be a highest score (in the case of assigning points for a match), or may be a lowest score, depending on the implementation desired. If the distance metric that signifies the closest match is closer than a threshold value to the stored credential <NUM> (e.g., the distance is smaller than a threshold), then the match determination logic <NUM> may return that a match is found. In an example, meeting the threshold value may require a perfect match. In other examples, the match determination logic identifies two distance metrics that signify the two closest matches with the stored credential <NUM> (e.g., a smallest distance and a second smallest distance). The match determination logic may then take the ratio of the two distance metrics and compare that to a threshold to determine whether there is a match. In some examples, the use of a threshold allows for authentication even when the entered credential <NUM> in the submitted symbols <NUM> is a less than perfect match for the sored credential <NUM>. This may allow for some level of noise tolerance where symbols of the entered credential <NUM> are replaced by noise symbols during transmission.

Access control <NUM> may then grant or deny access to the secured access-controlled resource based on the result from match determination logic <NUM>. For example, access control <NUM> may send a message to the computer device hosting the secured access-controlled resource to provide the results of the authentication attempt. In some examples, access control <NUM> may send a token to the user device or to the device hosting the secured access-controlled resource. In other examples, the access control <NUM> may provide the secured access-controlled resource. In some examples, the access control may send a signal to a physical device, which may provide access to a physical resource (e.g., unlock a door).

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user according to some examples of the present disclosure. At operation <NUM> the authenticator identifies a first set of symbols (e.g., characters) corresponding to a stored value, such as a credential (e.g., a username, password, encryption key). As used herein, a symbol is a unit of data, such as a character, a word, a byte, or other group of data. At operation <NUM>, the authenticator receives a second set of symbols (e.g., characters) to be compared with the stored value, the second set of symbols includes more symbols than the first set of symbols (e.g., noise characters). For example, the symbols may be entered credential symbols (e.g., a password) with additional noise symbols (e.g., characters) and the stored value may be a credential such as a password.

At operation <NUM> the authenticator determines if the second set of symbols includes a first subset of symbols matching the stored value. For example, the authenticator determines if the second set of characters includes a credential such as a password. If the second set of symbols does not include the stored value, then at operation <NUM>, access may be denied. If the second set of symbols includes the stored value, then processing moves to operation <NUM>. In some examples, to determine whether the second set of symbols includes the stored value the second set of symbols may be decomposed into a set of size m in-order vector combinations of the second set of values, where m is a number of symbols in the stored credential. The vectors reflect each of the possible in-order length m combinations of the submitted symbols. A distance metric may be calculated for each of the vectors that measures a distance between the stored value and each vector. The decision of whether the second set of symbols includes the stored value may be based on the distance metrics and whether at least one of the distance metrics is within a threshold distance of the stored value.

At operation <NUM>, the authenticator determines whether the second set of symbols includes a second subset of unspecified symbols in one or more unspecified positions within the second set of symbols. For example, the authenticator determines whether noise characters are added to the password characters. In some examples, the authenticator may ensure that additional symbols are entered to ensure that the user is secured from eavesdropping attacks. If there are no additional noise symbols added, then at operation <NUM> access is denied. Otherwise, access may be granted at operation <NUM>. It is noted that the authenticator does not specify for any authentication attempt where the noise symbols are to be placed, and what the noise symbols are. This protects the user by preventing eavesdropping of these locations.

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user according to some examples of the present disclosure. At operation <NUM>, the authenticator receives a set of submitted symbols to be authenticated during the authentication attempt. In some examples, the symbols are characters. In some examples, the received set of symbols includes more symbols than a first set of symbols corresponding to a stored value (such as a credential). For example, the entered characters include noise characters. At operation <NUM>, the authenticator creates a set of two or more vectors, each vector having a length corresponding to a length of an ordered vector comprising the first set of symbols corresponding to the stored value (e.g., the stored credential) and each vector comprising a different ordered combination of the received set of symbols, the different ordered combination of the received set of symbols ordered in a same order as the symbols were received. For example, if a received set of characters is {p,#,a,r,s,s} and the password (stored value) is {p,a,s,s} then a set of vectors of length <NUM> are created. In this example, the system would create a vector for each <NUM> character in-order combination of the received set of characters.

By in-order it is meant that the symbols in the vector maintain the ordering of the symbols in the submitted symbols relative to each other. Put differently, in the example above, if the character 'p' is in the vector, that character would always be first among the password characters (not considering noise symbols). An 'a' character in the vector would be either first (if 'p' was not in the vector) or second (if 'p' is in the vector) among the password characters (again, not considering noise symbols). So, in the above example, the following are valid vectors:.

At operation <NUM>, the authenticator may determine a set of distances between each respective vector and the ordered vector comprising the first set of symbols corresponding to the stored value. As previously noted, the set of distances may be determined by one or more distance metrics, such as a Levenshtein distance; a simple point total where points are added or subtracted based on differences in the symbols; or a statistical correlation. For example, a system utilizing a point value system may add a value of <NUM> to a score for symbol positions that do not match and a value of <NUM> to symbol positions that do match the stored value (e.g., the stored credential). In the example above, using this simple distance metric, the distances would be: {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>}. In still other examples, the vectors may simply be compared to the stored value to determine if there is a match. In yet additional examples, the distance metric may be a statistical correlation.

At operation <NUM>, the system may select a vector of the set of vectors based on the distance of the set of distances. For example, the system may select a vector with the shortest distance to the vector of the stored value. In the example above, the vector 'pass' has a distance of '<NUM>' and so that vector may be selected.

At operation <NUM>, the system may cause access to be granted to the computer resource based on a comparison of a value corresponding to the selected vector and a threshold. For example, a comparison of the distance value to a threshold. In other examples, the value may be a ratio of the distance value of the vector and a second vector (e.g., a second closest vector). The threshold may be predetermined or specified. In other examples, the threshold may be determined based on a length of the stored value. That is, for shorter stored values, the threshold may be set such that a closer match between the submitted symbols and the stored value is necessary to improve security. Thus, a stored value of three characters may have a lower threshold (where lower is a closer match) than a stored value of ten characters.

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user according to some examples of the present disclosure. At operation <NUM>, the client may cause display of a GUI. For example, a GUI shown in <FIG>. The GUI may have one or more data entry fields for entry of one or more symbols of one or more credentials by the user. For example, the GUI may comprise an input field for accepting characters of the requested authentication credential from an input device. In some examples, the GUI accepts the requested authentication credential in the form of a set of symbols (e.g., characters). Example input devices may include keyboards, on-screen keyboards, mouse inputs, touch inputs, biometric inputs, and the like. In some examples, the GUI may require that the set of symbols (e.g., characters) to include more symbols (e.g., characters) than a stored credential. For example, by checking a length of the characters entered by the user and checking that length against a length of a stored password. In some examples, the GUI may require that the set of characters include a threshold number of symbols more than a stored credential. The threshold may be prespecified or may be determined based on the length of the credential. For example, if the credential (e.g., password) is short, the system may require more noise symbols than if the credential is long. In other examples, the system may compare the values of the submitted symbols entered to the value of the symbols of the credential to determine if noise symbols were added.

In some examples, the client may check to make sure that the noise symbols (e.g., characters) are interspersed with the submitted credential. For example, if the noise symbols are at the beginning, end, or both beginning and end, but not interspersed within the submitted symbols, then the client may display an error. For example, if a measurement of spread of positions of the noise symbols throughout the credential symbols is below a threshold, then the client may show an error and make the user fix the submitted symbols such that the measurement of spread is above or equal to the threshold. Measurement of spread is detailed in more depth below.

If any of the above checks indicate that the submitted symbols (e.g., characters) of the user do not meet one or more of the above requirements, the client may display an error and require the user to correct the submitted symbols. The error may be displayed once the user submits the symbols through an input specifying that entry of the symbols (e.g., characters) is complete (e.g., pressing ENTER, clicking or tapping a button indicating that entry is complete, or the like). In other examples, the system may monitor the symbols entered as the user inputs them. For example, after a predetermined number of symbols (e.g., the length of the stored credential), the system may check the symbols for length, noise symbols, and/or measurement of spread, depending on the implementation. Example warnings to the user are shown in <FIG>.

At operation <NUM>, the client may accept the symbols (e.g., characters) entered by the user in the one or more data entry fields of the GUI. For example, after the user has submitted an input to indicate that the set of symbols is complete and the set of characters meets the requirements (e.g., the length is greater than the credentials; the submitted symbols include noise characters; the noise is interspersed; and/or the noise is interspersed and the spread measurement is above a threshold).

At operation <NUM>, the client may receive or identify an indication of whether access was granted or not. In some examples, the client may send the submitted symbols to a remote authenticator in a remote computing device, such as shown in <FIG>. The client may then receive the indication from the remote device of whether access was granted or not. In other examples, the client itself may include the authenticator and may perform the authentication as shown in <FIG>. In these examples, the indication may be an indication of whether access was granted or not from the authenticator that is received through a function return, interprocess communication, or the like.

At operation <NUM>, the system may determine whether the indication was that access was granted or denied. If access is denied, then at operation <NUM> the GUI may be caused to display a message that access was denied. In some examples, the user may retry the authentication. In some examples, a limit on the number of retry attempts may be implemented that prevents the user from retrying the authentication after a determined number of authentication failures within a determined amount of time.

If at operation <NUM>, access is granted, then at operation <NUM> the system may indicate that access has been granted. For example, the system may cause the GUI to display an indication that access was granted. In other examples, the system may simply remove the login screen and reveal access to the access-controlled resource. In other examples, the system may provide the requested access-controlled resource. At operation <NUM>, in some examples, the client may facilitate access to the requested secure access-controlled resource, such as by redirecting a user's browser to an address for the resource, executing a function that provides the resource, or the like.

<FIG> illustrates a diagram of an example GUI for allowing users to enter authentication credentials according to some examples of the present disclosure. In the example of <FIG>, there are two credentials, a username and a password. A user may select one of the boxes next to the requested credential and type in the symbols of the requested credential. For example, the user may type in the symbols of the username and/or password. When the user is finished, the user may enter an input specifying that entry of the characters is complete (e.g., pressing ENTER, clicking or tapping the submit button indicating that entry is complete, or the like).

<FIG> illustrate diagrams of example GUIs for allowing users to enter their authentication credentials according to some examples of the present disclosure. In <FIG>, the user has begun typing the user's password and the client has recognized that the user has not yet added any noise characters. The client then prompts the user with a warning. The warning may be in response to the user typing a threshold number of characters that does not include a noise character. The warning may disappear once the user enters a first noise character in some examples. In other examples, the client may calculate a ratio between noise characters and legitimate password characters. The warning may be displayed while the ratio is below a specified threshold ratio. In some examples, a warning may be displayed when a measure of spread is not within a target measure of spread (e.g., not above or below a threshold, or not within a specified range). In other examples, the warning may be shown in response to the user selecting "submit", and may prohibit the user from continuing until corrected.

In <FIG>, the user has begun typing a password, and the client has recognized that the password exceeds or falls short of a fixed length. In this example, the fixed length is required for the user's entry. The fixed length may include a fixed total length for all characters entered, or a fixed length of noise characters. In an example, the password entry box may limit the user such that more characters than the fixed limit are prevented from being entered. In an example, the client may prompt the user with a warning regarding the fixed length issue. The warning may disappear once the user enters a number of characters equal to the fixed length in some examples. In other examples, the fixed length may be a minimum length such that the warning may disappear when the fixed length or more characters are entered. In other examples, the warning may be shown in response to the user selecting "submit", and may prohibit the user from continuing until corrected.

In <FIG>, the user has begun typing a password, and the client has recognized that the entered characters do not include a subset of a valid password. For example, the entered characters may include the entire password or may not include any subset of the password. In this example, a subset of the valid password is required for the user's entry (and optionally not the entire valid password). In an example, the client may prompt the user with a warning regarding the fixed length issue. In an example, a minimum length of the subset may be required, and the warning may be displayed when the entered characters do not include a subset of the valid password of a sufficient length (e.g., meeting or exceeding the minimum length). The warning may disappear once the user enters a subset of the valid password. In other examples, the warning may be shown in response to the user selecting "submit", and may prohibit the user from continuing until corrected.

While the above-mentioned examples included an authenticator in either the user device or a remote device, in other examples, some functionality of the authenticator may be performed in the user device and other functionality may be performed in the remote device. For example, an authenticator in the user device may create the vectors and/or calculate the distance metrics and send the results to an authenticator on a remote device. In some examples, this may allow for distribution of the computational resources necessary for authenticating by having the client devices share some of the computational burden.

In some examples, the intermediate results may be protected in transit using encryption. In some examples, to prevent tampering, the results may be protected by a secured symmetric key given to a trusted application. The authenticator of the remote device may then use the corresponding key to unlock the results. By unlocking the results successfully, the authenticator on the remote device may trust that the results were produced by the trusted application. In some examples, to further prevent tampering, the authenticator on the user device may execute in one or more protected environments, such as a software guard extensions (SGX) environment or the like.

<FIG> illustrates a diagram <NUM> of a user device <NUM> and a remote device <NUM> with distributed authentication functions according to some examples of the present disclosure. <FIG> illustrates a system whereby the user device <NUM> performs part of the authentication process and provides intermediate calculations or partial results to the remote device <NUM>. For example, the user device <NUM> includes a local authenticator <NUM> which includes vector creator <NUM> and optionally distance metric calculator <NUM>. In these examples, the submitted symbols (e.g., characters) are submitted to the vector creator <NUM> which creates the set of vectors (e.g., those shown in <FIG>) and sends these to the remote device <NUM>.

In some examples, the local authenticator <NUM> may include a distance metric calculator <NUM> which may calculate the distances between the credential (e.g., password) and the vectors and send the distances to the remote device <NUM>. The remote device <NUM> includes a remote authenticator <NUM> which may include a match determination logic <NUM> and/or a distance metric calculator <NUM> (depending on whether the user device includes the distance metric calculator <NUM>). If the user device <NUM> provides the vectors to the remote device, the remote device <NUM> may provide those to the distance metric calculator <NUM> for calculation of the distance metrics. If the user device <NUM> provides the distance metrics (e.g., the user device <NUM> has the distance metric calculator <NUM>), the remote device receives those and passes them to the match determination logic. The match determination logic <NUM> utilizes the distance metrics to make a determination as to whether access is granted as previously described. As is shown in <FIG>, the secured access-controlled resource <NUM> may be on either the user device <NUM> or the remote device <NUM>.

While the above disclosed authentication system protects well against eavesdroppers, it may also be computationally expensive. In some examples, an attacker may attempt to cause a denial of service (DOS) attack against the authenticator by submitting symbols of a long length. For example, an attacker may submit an authentication attempt of <NUM> characters. If the password is only <NUM> characters, there are many in-order combinations of length ten of the submitted symbols. The large number of vectors generated may also trigger many distance measurements to be generated. These operations may utilize large amounts of processing and memory resources of the authenticator. A sophisticated attack may feature hundreds of such attack authentication attempts that may overwhelm the authenticator and prevent the authentication of legitimate users as the authenticator may be too busy servicing illegitimate attacks to attend to the legitimate authentication.

In some examples, to prevent this problem, the client and/or authenticator may reject authentication requests with submitted symbols (e.g., submitted characters) that do not meet length requirements. For example, submitted symbols with a length that is above a length threshold may be accepted. The length threshold may be measured against a total length of the submitted symbols (e.g., password characters and noise characters), a length of the noise symbols only, a length of the password symbols only, a ratio of noise symbols to password symbols or the like. In other examples, the length may be a specified length. That is, the submitted symbols, the noise symbols, and/or the credential symbols may be required to be of a specified length. The rejection may be handled prior to creating the vectors, such that a rejected authentication attempt is not processed to create the vectors.

The present disclosure solves a technical problem of providing secure access to computing resources using a secure password that is resistant to keyloggers, eavesdroppers, and man-in-the middle attacks as well as being resistant to denial of service attacks. The entered symbols are limited to the threshold to prevent overly complicated calculations at the authenticator.

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user with a size limit according to some examples of the present disclosure. At operation <NUM> the authenticator identifies a first set of symbols corresponding to a stored value, such as a password, other credential, or other stored value. At operation <NUM>, the authenticator receives a second set of symbols to be compared with the stored value, the second set of symbols including more symbols than the first set of symbols. For example, the symbols may be entered password characters.

At operation <NUM>, the system may determine whether the symbols meet one or more length criteria. If the symbols meet the one or more length criteria, then processing continues to operation <NUM>, otherwise authentication is denied at operation <NUM>. Length criteria may be minimum lengths, maximum lengths, or ranges of minimum and maximum lengths.

In some examples, the symbols checked against the criteria at operation <NUM> are the submitted symbols (e.g., the characters entered by the user including both the credential characters and the noise characters) and the criteria is that the number of submitted symbols are less than a threshold - e.g., operation <NUM> is determining if the total length of the submitted symbols is less than a threshold length. Thus, if a user enters <NUM> characters and the threshold is <NUM>, the authentication would fail the determination at operation <NUM> and access would be denied at operation <NUM>. In some examples, there may be a required minimum total length in addition to a maximum length (e.g., to ensure that enough noise symbols are entered).

In another example, the symbols checked against the criteria at operation <NUM> are the noise symbols and the criteria includes a restriction that the number of noise symbols are less than a threshold. That is, operation <NUM> is determining if the number of noise symbols is less than the threshold number of noise symbols. This may be accomplished by subtracting a total number of symbols in the submitted symbols from a length of the credential and comparing the result to the threshold. For example, if the submitted symbols are <NUM> symbols long and the stored credential is <NUM> symbols long, then (<NUM>-<NUM>) = <NUM> is compared with the threshold. If the threshold is <NUM> or more, then processing may continue, otherwise, the access is denied at operation <NUM>. In other examples, a number of noise symbols may be determined by removing the symbols corresponding to the credential from the submitted symbols and then comparing a count of the remaining symbols to the threshold. For example, when the credential is a password and the valid password is "pass" and the submitted symbols are characters entered by the user and are "pass12345" the characters 'p', 'a', 's', 's' are removed leaving "<NUM>", which is five characters long. Five is then compared with the threshold. If five fails to meet or exceed the threshold, then at operation <NUM> access may be denied. As noted above, in some examples a minimum number of noise symbols may also be required such that both a minimum and a maximum number of noise symbols may be required.

In other examples, rather than a threshold length, the length criteria is an exact symbol count (e.g., the amount of symbols is no more and no less than the specified symbols). For example, the submitted symbols may be required to be of a preset count. In other examples, the noise symbols may be required to be of a preset count. In yet other examples, a ratio of noise symbols to credential symbols may be required to be of a preset ratio. For example, when the submitted symbols are required to be ten symbols, and the credential is "pass" then the system may require four credential symbols (e.g., characters) and six symbols to be added as noise symbols (e.g., characters) as the total (noise and credential symbols) must equal ten symbols. For example, if the total count of the submitted symbols is not equal to the preset count, access may be denied. In some examples, the preset count may be global for all authentication attempts or may be specified for each authentication attempt.

At operation <NUM> the authenticator determines if the second set of symbols includes a first subset of symbols matching the stored value. If the second set of symbols does not include a first subset of symbols matching the stored value, then access is denied at operation <NUM>. If the second set of symbols includes a first subset of symbols matching the stored value, then processing continues at operation <NUM>. For example, the authenticator searches for the stored credential in the second set of symbols. As previously explained this may include splitting the submitted symbols into vectors and calculating distances between each vector and the stored credential. The distances may be used to determine whether the second set of symbols includes a first subset matching the stored value (e.g., the stored credential).

At operation <NUM>, the authenticator may determine whether the second set of symbols includes a second subset of unspecified symbols. That is, the authenticator ensures that noise symbols have been added to the submitted symbols. In some examples, this operation may have already been performed as the results of the symbols meeting the length criteria at operation <NUM> may ensure a minimum number of noise symbols. If noise symbols have been added, then at operation <NUM>, access may be granted. If noise symbols have not been added, then at operation <NUM>, access may not be granted. As described herein, the authenticator may also require that the noise symbols meet a criteria related to a measure of spread, that there be a minimum number of noise symbols, and/or the like.

It is noted that the authenticator does not specify for any authentication attempt where the noise characters are to be placed, and what the noise characters are. This protects the user by preventing eavesdropping of these locations. By requiring a maximum amount of submitted symbols, external attacks on the authenticator that may deny service may be avoided.

As noted previously, in some examples the system may force the user to enter noise symbols within the entered symbols of the credential. This may prevent the user from simply typing their normal credentials without the additional protections the noise symbols offer against eavesdroppers. The addition of noise symbols (such as noise characters) may be enforced at the authenticator or the client. For example, at the client, the client may have a local copy of the user's credential and may compare the submitted symbols to the credential to determine whether the submitted symbols include noise symbols that are interleaved with the credential symbols. The authenticator may reject authentication attempts where the submitted symbols do not include the noise symbols.

In examples in which the client checks for the insertion of noise symbols, determining whether the entered symbols include noise characters may include determining that a minimum number of symbols were entered (e.g., a sum of the password length and a threshold number of noise characters). In some examples, only a single noise symbol may be required to be entered, but in other examples a threshold amount of noise symbols may be required to be entered. In some examples, the system may combine a length cap on submitted symbols with a forced character insertion such that the user must input a number of symbols that falls within a minimum and a maximum number of symbols.

In some examples, to prevent users from simply repeating symbols of the credential (which may not be as secure as random symbols), the system may compare the credential to the submitted symbols. For example, the system may require that the noise symbols be symbols that are not present in the credential symbols. Thus, if the credential is a password with characters "pass" then the noise characters must be characters other than 'p' 'a' 's' 's'. If the noise symbols include symbols from the credential, authentication may be denied. In some other examples, rather than making a direct comparison, some repeated characters from the credential may be allowed, however a difference metric may be calculated by the client that quantifies how different the stored credential is from the submitted symbols. A minimum difference value may be required for authentication to be successful. The client may enforce these standards by refusing to pass the submitted symbols to the authenticator if they do not meet these standards.

In examples in which the authenticator enforces the insertion of noise symbols, determining whether the submitted symbols include noise symbols may be done similarly to that described for the client, such as determining that a minimum number of symbols were entered (e.g., a sum of the password length and a threshold number of noise characters). In other examples, the authenticator may utilize the distance metric to quickly determine whether noise symbols were inserted. For example, the authenticator may require that at least one distance metric be above a threshold difference (e.g., not a perfect match). In other examples, the distance metric may be used to quickly determine whether a user has previously used the exact same submitted symbols. For example, the system may compare one or more distance metrics to one or more past distance metrics of vectors created from past authentication attempts. If there is an exact match for a previous distance metric from a previous authentication attempt, the system may reject the authentication request.

Users may not always comply with the goals of the present system - either intentionally or inadvertently by choosing locations for noise symbols that are predictable and not random. For example, users may add noise symbols at the front, back, or both the front and the back - rather than randomly interspersed amongst the credential (e.g., password). In so doing, they may not achieve the level of protection offered by the disclosed authentication scheme as they may attempt to simply enter the noise before, after, and/or before and after the legitimate credential. If the user's introduction of noise symbols in the credential is not well-distributed, an eavesdropper may still discern a user's credential through observing patterns of symbols across multiple authentication attempts.

As an example, consider the following sequences of authentication attempts where the user's credential is "pass":.

In these examples, it may be possible for an eavesdropper (even a shoulder-surfer) to observe multiple log-in attempts and discern a user's credential as the common characters between each authentication attempt may be quickly separated from the noise symbols by observation. To prevent this, the system may determine one or more metrics for determining how well distributed the noise symbols are within the credential (or equivalently, how well distributed the credential is within the noise symbols). In some examples, a metric, termed a measure of spread may quantify how evenly one set of symbols is distributed within a second set of symbols.

The system (either the client or the authenticator) may require that the measure of spread of the positions of noise symbols in credential symbols be above a specified threshold to ensure that the noise symbols are distributed throughout the credential. In some examples, the system (either the client or the authenticator) may specify that the measure of spread also be below a specified threshold to ensure that perfect distributions of noise symbols throughout the credential are also avoided, as a perfect distribution may also be easy for an eavesdropper to figure out. The system may desire to obtain what appears to be a random distribution of noise symbols in credential symbols by requiring a measure of spread to be within a particular range.

In some examples, the system may also store a history of a calculated measure of spread for past authentication attempts for a specified number of logins or time frame. The system may require the measure of spread to be varied over time, such that authentication attempts with submitted symbols that are either a same measure of spread, or are similar (e.g., within a threshold number) to each other may be rejected. This may assist in promoting randomness in distributing the noise symbols. In some examples, the system may statistically analyze a user's measurements of spreads for past authentication attempts. Example statistical analysis include calculations of a standard deviation of the measurements of spread. If the standard deviation is lower than a threshold, the system may adjust the target range of the measurement of spread to move the standard deviation toward the threshold. In this way, the system monitors the distribution of noise symbols in the password symbols over time to better achieve a random appearance.

In some examples, when users are entering in their credentials, the system may calculate, in real time, a measure of spread and provide an indication of whether the user is within the desired range. This may be a simple indication that the user is within the acceptable range, or that the user is not within the acceptable range. If the user is not within the acceptable range, the system may provide tips on moving to the acceptable range (e.g., "insert more noise characters" or "remove some noise characters").

The present disclosure thus solves a technical problem of providing secure access to access-controlled resources using a secure credential that is resistant to keyloggers, eavesdroppers, and man-in-the middle attacks. By enforcing good noise symbol distribution, the system may ensure that users take advantage of the security enhancing aspects of the present disclosure by ensuring that the credentials are not easily deciphered from the submitted symbols. For example, the present system may ensure that the noise symbols appear random, rather than following a discernable pattern.

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user with a measure of spread criteria according to some examples of the present disclosure. At operation <NUM> the authenticator identifies a first set of symbols corresponding to a stored value, such as a password. At operation <NUM>, the authenticator receives a second set of symbols to be compared with the stored value, the second set of symbols includes more symbols than the first set of symbols. For example, the symbols may be entered password characters.

At operation <NUM> the authenticator determines if the second set of symbols includes a first subset of symbols matching the stored value. For example, the authenticator determines if the second set of characters includes the stored credential (e.g., password). If the second set of characters does not include the stored credential, then at operation <NUM>, access may be denied. If the second set of characters includes the stored credential, then processing moves to operation <NUM>. In some examples, to determine whether the second set of characters includes the stored credential the second set of symbols may be decomposed into a set of size m in-order vector combinations of the second set of character, where m is a number of symbols in the stored credential. The vectors reflect each of the possible in-order length m combinations of the submitted symbols. A distance metric may be calculated for each of the vectors that measures a distance between the stored credential and each vector. The decision of whether the second set of characters includes the stored credential may be based on the distance metrics and whether at least one of the distance metrics is within a threshold distance of the stored credential.

At operation <NUM>, the authenticator determines whether the second set of symbols includes a second subset of unspecified symbols in one or more unspecified positions within the second set of symbols. For example, the authenticator determines whether noise characters are added to the password characters. In some examples, the authenticator may ensure that additional characters are entered to ensure that the user is secured from eavesdropping attacks. If there are no additional noise characters added, then at operation <NUM> access is denied. Otherwise, processing may continue at operation <NUM>. It is noted that the authenticator does not specify for any authentication attempt where the noise characters are to be placed, and what the noise characters are. This protects the user by preventing eavesdropping of these locations.

At operation <NUM> the system may determine whether a measure of spread of respective positions of the first subset or the second subset within the second set of symbols is within a threshold range or otherwise meets one or more specified criteria. Thus, the system may (depending on the design) determine how distributed the first subset is within the second set of symbols (e.g., how distributed the password characters are), or, how distributed the noise symbols are within the second set of symbols.

Example measurements of spread include calculating a greatest distance between respective positions of subsequent ones of the first or second subset of symbols within the second set of symbols. For example, if the password is "pass" and the user enters 'p1a2s3s4', the measurement of spread would be <NUM>. In these examples, the system may require a minimum measure of spread - e.g., that the greatest distance between respective positions of subsequent ones of the second subset of symbols within the second set of symbols be less than a threshold. In other examples, the measurement of spread may be an average distance between respective positions of subsequent ones of the first or second subset of symbols within the second set of symbols.

In yet other examples, the measurement of spread may be a variance of the respective positions of the first or second subsets of symbols within the second set of symbols. In still other examples, the measurement of spread may be a standard deviation of the respective positions of the first or second subsets of symbols within the second set of symbols.

In some examples, the threshold range may be an upper threshold, a lower threshold, or an upper and a lower threshold. The thresholds may be specified, or may be derived. For example, the thresholds may be derived from a length of the credential. For example, a higher level of spread may be required for shorter credentials (to increase security) than longer credentials, or vice versa. In some examples, both an upper bound and a lower bound ensures that the noise symbols are noisy - that is, they do not conform to an easy to decipher pattern. For example, a case where a user's password is "pass" and the user enters "p1a2s3s4" may be less secure than a user entering "p12as22s" because the every-other-symbol insertion of noise symbols in the former may be more predictable than the more random insertion in the latter. By requiring the spread to be higher than a minimum, but not a perfect spread, the system may require more randomness.

If at operation <NUM>, the measure of spread is not within the threshold range, then access may be denied at operation <NUM>. If at operation <NUM>, the measure of spread is within the threshold range, then at operation <NUM>, access may be granted.

In an example, spread of noise in a password within a set of entered characters may be determined by creating a set of vectors of the entered characters. The set of vectors may be generated as described herein. A distance metric from one or more of the set of vectors to vectors of the password may be compared. In an example, an average, a median, or a total vector distance may be evaluated and compared to a threshold. When the average, median, or total distance transgresses the threshold, the set of entered characters may be determined to have sufficient spread. In another example, a subset of the set of vectors may be used (e.g., only vectors that are between two thresholds, a "close" threshold and a "far" threshold may be used), and the subset may be required to have a minimum number of vectors.

In yet another example, the subset of vectors may be generated by taking sequential, in-order characters of a total length equal to the password. For example, the password may be "pass," and the entered characters "p#arss," which is an example with noise sufficiently spread throughout. The set of vectors may be constructed in this example to be "p#ar", "#ars", and "arss. " None of these are particularly close, distance-wise to "pass". An example of entered characters having insufficient spread would be "#rpass. " In this example, the set of vectors may include "#rpa", "rpas", and "pass. " These vectors are closer in distance to the password (including the password itself), thus the entered characters may be determined to have insufficient spread.

<FIG> illustrates a diagram of a data flow <NUM> of an authentication with additional, unspecified noise symbols according to some examples of the present disclosure. <FIG> is similar to <FIG>, except in <FIG>, the authenticator <NUM> includes a spread checker <NUM>. Spread checker <NUM> may calculate a measure of spread that quantifies how well distributed the user entered noise symbols <NUM> are within the submitted symbols <NUM> (or how well distributed the credential symbols are within the submitted symbols <NUM>). Spread checker <NUM> may be included in authenticator <NUM>, either in a user device <NUM>, or a remote device <NUM> as shown in <FIG>, and <FIG>. Spread checker <NUM> may also be part of the client <NUM>. For example, the measure of spread may be calculated as the user enters the credential and may give feedback to the user in real time indicating whether the measure of spread is within an acceptable range.

Spread checker <NUM> may calculate a spread of either the noise symbols <NUM> (e.g., characters) within the total submitted symbols <NUM> entered by the user or the credential symbols <NUM>, <NUM>, and <NUM> within the total submitted symbols <NUM> entered by the user. As noted previously, example measurements of spread include calculating a greatest or average distance between password or noise characters, a variance, a standard deviation, or the like.

Spread checker <NUM> may compare the calculated spread to determine whether the measure of spread meets a specified criteria. For example, the criteria may be whether the measure of spread is above a first threshold. In other examples, the criteria may be whether the measure of spread is below a second threshold. In yet other examples, the criteria may be whether the measure of spread is both above a first threshold and below a second threshold (and thus in a desired range). If the result is that the measure of spread of the submitted symbols <NUM> meets the criteria, then processing continues to vector creation with vector creator <NUM>. If the measure of spread does not meet the criteria, then the determination may be made by match determination logic <NUM> that authentication is denied.

In some examples, an eavesdropper may not try and decipher the password from the noise characters. Instead, the eavesdropper may utilize a replay attack whereby the entire entered sequence is captured and later "replayed" in its entirety, including the noise characters. To prevent this, in some examples, the system may take measures to detect and reject authentication attempts that are identical or similar to past authentication attempts.

For example, the authenticator may store the submitted symbols for a plurality of past authentication attempts. When a new authentication attempt is made, the newly received submitted symbols are compared to stored submitted symbols for past authentication attempts. If the newly received submitted symbols for the current authentication attempt match, or are within a specified threshold level of similarity of (to prevent simple changes), one of the stored past submitted symbols for past authentication attempts, the system may reject the authentication attempt.

The system may store the submitted symbols for the plurality of past authentication attempts for a specified time period (e.g., the last day, last week, last month, and the like), a specified number of authentication attempts, or the like.

In other examples, instead of storing past submitted symbols, the system may store one or more of the distance metrics or measurements of spread of past authentication attempts. For example, the system may store the two or three closest distance metrics for each authentication attempt. If one or more distance metrics and/or spread measurements of a current authentication attempt are within a threshold difference of one or more distance metrics and/or spread measurements of past authentication attempts, then the present authentication attempt may be rejected. By storing the distance metrics or spread measurements instead of the submitted symbols, the system may reduce the amount of storage needed to prevent replay attacks.

In some examples, an eavesdropper may have access to the user's communications over multiple authentication attempts. For example, keyloggers and man-in-the middle attacks may observe the user over many authentication attempts. An attacker may be able to discern a user's password by detecting common characters across multiple authentication attempts. Even if the system enforces a random-like distribution of noise symbols in the credential, sophisticated algorithms may find patterns in the captured data.

To prevent this, the system may force the user to enter a subset of their credential. For example, the user's password may be "password" and the user may authenticate with "pass," "sswor," "word," or the like. In some systems, with the user's password as "password" other combinations such as "pawo" or "psrd" may be used (e.g., in a same order as characters in "password", but not necessarily sequential). In some examples, the system may require the user to use a different credential subset each authentication attempt. This makes it more difficult for eavesdroppers to observe the user's credential by detecting common symbols (e.g., characters) across multiple authentication attempts. In an example, the different credential subset may be repeated after a number of non-uses or a period of time (e.g., after <NUM> different subsets, a first entered subset may be repeated or after six months an already entered subset may be repeated).

The system may enforce a minimum subset length (e.g., the subset meets a minimum number of characters, a minimum percentage of the total password, or the like). The system may enforce a rule that a same subset may only be used a specified number of times over a specified number of authentication attempts (or a specified time period). For example, a same credential subset may only be used twice over ten authentication attempts. In some examples, the subset may be required to be comprised of contiguous symbols, but in other examples, skipping of symbols may be allowed. In some examples, the subset must be in order. That is, if the user's password is "password," the subset "pssord" is a valid subset, but "dpssor" is not.

The present disclosure thus solves a technical problem of providing secure access to access-controlled resources using a secure credential that is resistant to keyloggers, eavesdroppers, man-in-the middle, and replay attacks. This is accomplished through the introduction of user-specified random noise symbols that are introduced at user-specified random locations. The authenticating device decomposes the submitted symbols into a plurality of vectors and utilizes a distance metric to determine if authentication should be granted. By utilizing credential subsets in addition to noise symbols, the system may make it more difficult for attackers that are eavesdropping on the user to ascertain the user's credential.

<FIG> illustrates a diagram of a data flow <NUM> of an authentication attempt with additional, unspecified noise symbols and enforced credential subsets according to some examples of the present disclosure. The credential <NUM> (e.g., password) may comprise six symbols in the form of characters P1-P6. In the example of <FIG>, the user has entered P2, P3, and P4 as subset credential symbols <NUM>. The user, when entering the credential adds one or more noise symbols <NUM> (e.g., characters) to the subset. In the example shown in <FIG>, for ease of description, only one noise symbol <NUM> is added. The submitted symbols <NUM> entered by the user, includes the subset credential symbols <NUM> along with the one or more noise symbols <NUM> interspersed into the credential characters.

The authenticator <NUM> includes a subset creator <NUM> that identifies a plurality of ordered vectors (called credential subset vectors) comprising ordered subsets of the stored credential <NUM> of the user. In examples in which subsets must be of a minimum number of symbols, the subset creator <NUM> creates credential subset vectors of the minimum size and greater (up to either the size of the stored credential <NUM> or a maximum subset size). For example, if the minimum size is <NUM> characters, then each of the credential subset vectors is five or more characters and the credential subset vectors comprise a set of all possible subsets of the stored credential <NUM> of five or more characters (optionally as a strict subset, e.g., not including the credential <NUM> in its entirety).

Check vector creator <NUM> receives the submitted symbols <NUM> entered by the user and creates a plurality of vectors from the submitted symbols <NUM>, each having a length corresponding to a length of a credential subset vector created by the subset creator <NUM>. These vectors may be called "check vectors. " The plurality of check vectors reflect each of the possible length m in-order, combinations of the submitted symbols <NUM>, where m are valid subset lengths of the stored credential. The order of the symbols in each of the check vectors is a same order as an order of the credential symbols in the submitted symbols <NUM>. As shown in <FIG>, m are vectors of length three, four, and five vectors. In other examples, m may be different lengths. For example, a user may submit a credential length with the submitted symbols <NUM> (e.g., P2,N1,P3,P4 plus "<NUM>"). In another example, a user interface may indicate a credential length to be submitted (e.g., a random number greater than some minimum but less than the total credential length, or a number assigned by a credentialing service, such as the access control <NUM>).

Each check vector and each credential subset vector is then passed to a distance metric calculator <NUM> that calculates a distance between each combination of the credential subset vectors and each of the plurality of check vectors. In other examples, distance metric calculator <NUM> calculates a distance between each same-sized combination of the credential subset vectors and each of the plurality of check vectors. In some examples, the distance metric may be a Levenshtein distance. In other examples, a distance metric may compare each symbol of each check vector to the corresponding symbol of each credential subset vector. If the symbols match, then the score may not be incremented. If the symbols do not match, the score may be incremented. In other examples, a higher score reflects a better match and thus symbols that match may cause the score to be incremented and symbols that do not match may cause no change in the score or may cause the score to be decremented. In still other examples, the distance metric may be a correlation, such as a Pearson correlation coefficient.

The distance metrics are then passed to the match determination logic <NUM>. In some examples, the match determination logic <NUM> identifies the distance metric that signifies a closest match between a check vector and one of the credential subset vectors (e.g., a smallest distance). This may be a highest score (in the case of assigning points for a match), or may be a lowest score, depending on the implementation desired. If the distance metric that signifies the closest match is closer to one of the credential subset vectors than a threshold value (e.g., the distance is smaller than a threshold), then the match determination logic <NUM> may return that a match is found. In other examples, the match determination logic identifies two distance metrics that signify the two closest matches with the credential subset vectors (e.g., a smallest distance and a second smallest distance). The match determination logic <NUM> may then take the ratio of the two distance metrics and compare that to a threshold to determine whether there is a match.

In some examples, the check vector creator <NUM> may verify that the submitted symbols <NUM> includes a subset, but not all the stored credential <NUM>. For example, the check vector creator <NUM> may determine a count of the number of the symbols in the submitted symbols that match, in order, symbols from the credential. In some examples, the check vector creator <NUM> may ensure this is within an acceptable range. For example, the check vector creator <NUM> may compare this number of symbols to a minimum threshold (to ensure a minimum subset size) and a maximum threshold (to ensure that the subset is not too close to the entire password). If the number of symbols is within this range, the check vector creator <NUM> may determine that authentication proceeds. If the number of symbols is not within the range, the check vector creator <NUM> may cause authentication to be denied.

In some examples, the presence of a subset (and not the entire credential) may be determined by verifying that the check vector with the closest distance metric to any of the credential subset vectors is within a desired distance range. The range may enforce a minimum closeness and a maximum closeness. This ensures that the subset is complete enough to constitute an authentication, but not the entire (or almost entire) credential.

In yet another example, a ratio of the distance of the vector with a closest distance and the distance of the vector with a next closest distance may be compared to a minimum threshold. In this example, the system may also enforce a maximum threshold on the distance of the vector with the closest distance. In this example, a hybrid of thresholds is used to enforce the minimum and maximum, with the minimum threshold used on the ratio and the maximum threshold used on the distance itself.

The check vector creator <NUM> may verify that the subset meets a minimum length. For example, the minimum length may be a specified length, or may be calculated based on the length of the stored credential <NUM>. For example, the shorter the credential length, the shorter the minimum subset length may be. In some examples, the minimum subset length may increase as the credential length increases until a defined maximum, at which point longer credential lengths do not increase the minimum subset length.

In some examples, the check vector creator <NUM> may enforce duplicate entry restrictions such that that credential subsets that are entered are compared across authentication attempts to determine if the user is utilizing a same subset frequently (e.g., over a threshold occurrence). If the user's use of a particular subset transgresses a threshold rate of occurrence, the authenticator <NUM> may reject the authentication attempt. In some examples, the rate of occurrence may be defined as a number of usages over a specified amount of time (e.g., the past day, week, month) or as a specified number of login attempts.

In some examples, the threshold frequency may be based on a length of the stored credential <NUM>. For example, depending on the length of the stored credential <NUM>, there may only be x number of valid subsets of a minimum length l. In some examples, the threshold frequency may be set based on x, such as x divided by <NUM>, or x, or x - a configurable or specified margin.

In some examples, in addition to enforcing a requirement of a different subset, the check vector creator <NUM> may enforce a requirement that the noise symbols <NUM> may be different or be interspersed in different locations of the entered credentials <NUM> across multiple authentication attempts.

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user with a credential subset according to some examples of the present disclosure. At operation <NUM> the authenticator identifies a first set of symbols corresponding to a stored value, such as a credential. At operation <NUM>, the authenticator receives a second set of symbols to be compared with the stored value, the second set of symbols includes more symbols than the first set of symbols. For example, the symbols may be entered password characters.

At operation <NUM>, the authenticator may determine if any subset of the second set of symbols matches the symbols of the stored value. For example, the authenticator may determine a plurality of ordered vectors (called credential subset vectors) comprising ordered subsets of the stored credential of the user of all possible lengths greater than a minimum subset length. For example, if the stored credential is "password" and the minimum subset length is three (in some examples, skipping symbols is not allowed, but other examples may allow for skipping, such as "pwd" in this example) the credential subset vectors would be all possible in-order subsets of three, four, five, six, seven, and eight characters. In some examples, a maximum subset size may also be specified. In these examples, the credential subset vectors may be limited to a maximum size to enforce the requirement that the credential entered be a subset (and not the entire credential). The maximum size may be specified (e.g., by an administrator) or may be calculated based on the size of the credential. In the above example where the credential is "password," if the maximum subset size limit is six, then the credential subset vectors would be all possible in-order subsets of three, four, five, and six symbols (examples below shown where skipping is prevented for ease of readability):.

The authenticator then creates a plurality of vectors (check vectors) from the second set of symbols, each vector having a length corresponding to a length of a corresponding credential subset vector. The check vectors reflect each of the possible in-order, combinations of the second set of symbols of a length corresponding to the length of a corresponding credential subset vector. For example, if there are four sets of credential subset vectors, with respective lengths of <NUM>, <NUM>, <NUM>, and <NUM> symbols, then a first plurality of check vectors are created with all possible three symbol long, in-order combinations of the second set of symbols; a second plurality of check vectors are created with all possible four symbol long, in-order combinations of the second set of symbols; a third plurality of check vectors are created with all possible five symbol long, in-order combinations of the second set of symbols; and a fourth plurality of check vectors are created with all possible six symbol long, in-order combinations of the second set of symbols. By in-order, it is meant that an order of the characters in each of the check vectors is a same order as an order of the symbols in the second set of symbols.

In some examples, a distance between each of the credential subset vectors of a particular length and each of the plurality of check vectors of a same particular length is calculated. The distance quantifies a difference between each check vector and each credential subset vector. In other examples, a distance between each combination (regardless of size) of the credential subset vectors and each of the plurality of check vectors is calculated.

The authenticator then determines if the second set of symbols includes a first subset of symbols matching a portion of the stored value. For example, the authenticator determines if the second set of symbols includes a subset of the stored credential (e.g., password). In some examples, to determine whether the second set of symbols includes the first subset matching a portion of the stored value, the system may utilize the distance metrics and whether at least one of the distance metrics is within a threshold distance of the credential subset vectors. If the second set of characters does not include a subset of the stored credential, then at operation <NUM>, access may be denied. If the second set of characters includes a subset of the stored credential, then processing moves to operation <NUM>.

At operation <NUM>, the authenticator determines whether the second set of symbols includes a second subset of unspecified symbols in one or more unspecified positions within the second set of symbols. For example, the authenticator determines whether noise symbols are added to the credential. In some examples, the authenticator may ensure that additional characters are entered to ensure that the user is secured from eavesdropping attacks. If there are no additional noise symbols added, then at operation <NUM> access is denied. Otherwise, access may be granted at operation <NUM>. It is noted that the authenticator does not specify for any authentication attempt where the noise characters are to be placed, and what the noise characters are. This protects the user by preventing eavesdropping of these locations.

<FIG> illustrates a flowchart of a method <NUM> of authenticating a user with a credential subset according to some examples of the present disclosure. At operation <NUM> the authenticator may receive a set of symbols (e.g., submitted symbols) as part of an authentication request (e.g., an access request). At operation <NUM>, the authenticator determines that no subset of the set of submitted symbols exactly matches a stored value (e.g., a credential such as a password). This ensures that the entered credential is a subset and not the entire credential. If there is a subset of the received set of symbols that exactly matches the stored value, in some examples, authentication may fail.

At operation <NUM>, the authenticator may identify ordered vectors comprising ordered subsets of the stored value having a length less than the length of the stored value (e.g., the credential subset vectors). At operation <NUM>, the authenticator creates a plurality of check vectors having lengths corresponding to the lengths of the credential subset vectors. At operation <NUM>, the authenticator may determine a set of distances between the plurality of check vectors and the credential subset vectors. As noted, in some examples, the set of distances comprises distances between each combination of check vectors and credential subset vectors, but in other examples, the set of distances comprises only distances between each combination of same-sized check vectors and credential subset vectors (e.g., check vectors of size z and credential subset vectors of size z).

At operation <NUM> the authenticator may select a check vector corresponding to a smallest distance. At operation <NUM>, the authenticator may cause access to be granted to a secure access-controlled resource based on a comparison of a value corresponding to the selected vector and a threshold. For example, the smallest distance value corresponding to the selected vector and the threshold. In other examples, a ratio of the smallest distance corresponding to the selected vector and a second smallest distance corresponding to the selected vector or a second check vector may be compared with a threshold.

<FIG> illustrates a flowchart of a method <NUM> of an authentication attempt using subsets according to some examples of the present disclosure. At operation <NUM>, the client may cause display of a GUI. For example, a GUI shown in <FIG>. The GUI may have one or more data entry fields for entry of one or more symbols of one or more credentials by the user. For example, the GUI may comprise an input field for accepting characters of the requested authentication credential from an input device. In some examples, the GUI accepts the requested authentication credential in the form of a set of symbols (e.g., characters). Example input devices may include keyboards, on-screen keyboards, mouse inputs, touch inputs, biometric inputs, and the like. In some examples, the GUI may require that the set of symbols (e.g., characters) to include more symbols (e.g., characters) than a stored credential. For example, by checking a length of the characters entered by the user and checking that length against a length of a stored password. In some examples, the GUI may require that the set of characters to include a threshold amount of symbols more than a stored credential. The threshold may be prespecified or may be determined based on the length of the credential. For example, if the credential (e.g., password) is short, the system may require more noise symbols then if the credential is long. In other examples, the system may compare the values of the submitted symbols entered to the value of the symbols of the credential to determine if noise symbols were added.

In some examples, the client may check to make sure that the noise symbols (e.g., characters) are interspersed with the submitted credential. For example, if the noise symbols are at the beginning, end, or both beginning and end, but not interspersed within the submitted symbols, then the client may display an error. For example, if a measurement of spread of the noise symbols throughout the credential symbols is below a threshold, then the client may show an error and make the user fix the submitted symbols such that the measurement of spread is above or equal to the threshold. Measurement of spread is detailed in more depth below.

In some examples, the client may verify that the submitted symbols do not exactly match the stored credential, but instead includes a subset. For example, the client may compare the symbols as they are being entered with the stored credential to make sure that the user has entered a subset of a minimum and/or maximum length. If the submitted symbols do not include a subset of the credential, the GUI may display an error and make the user fix the submitted symbols such that the submitted symbols include a subset of the stored credential.

If any of the above checks indicate that the submitted symbols (e.g., characters) of the user do not meet one or more of the above requirements, the client may display an error and require the user to correct the submitted symbols. The error may be displayed once the user submits the symbols through an input specifying that entry of the symbols (e.g., characters) is complete (e.g., pressing ENTER, clicking or tapping a button indicating that entry is complete, or the like). In other examples, the system may monitor the symbols entered as the user inputs them. For example, after a predetermined number of symbols (e.g., the length of the stored credential), the system may check the symbols for length, noise symbols, and/or measurement of spread, depending on the implementation. An example warning to the user is shown in <FIG>.

At operation <NUM>, the client may accept the symbols (e.g., characters) entered by the user in the one or more data entry fields of the GUI, where the set of symbols includes more characters than the stored credential and includes no subset of the set of characters that exactly matches the stored credential. For example, after the user has submitted an input to indicate that the set of symbols is complete and the set of characters meets the requirements (e.g., the length is greater than the credentials, the submitted symbols include noise characters, the noise is interspersed, and/or the noise is interspersed and the spread measurement is above a threshold). In an example, the requirements may not require that the length of the set of characters be greater than the credentials. For example, when the password is "password," a subset entered by the user with noise may be "p1a2s3s," which is fewer characters than "password" but may still be sufficiently secure.

In some examples, the various features described above may be implemented alone, or in combination. For example, the system may require noise characters, enforce a maximum number of total characters, require a subset, require a noise character distribution that is within a range of measurement of spread, and require that the submitted symbols <NUM> not be duplicated. In other examples, only certain features may be implemented, and others may not be implemented. In yet other examples, the features and requirements implemented may be configurable by an end user, an administrator, or the like. The preceding disclosure focused on the user of the authentication techniques to authenticate a user's credentials. However, as noted the credential is but one type of stored value that may be compared. The present techniques may be used generally to verify a received value to a stored value. In addition, in various flowcharts, the order of operations may be exemplary. For example, in <FIG>, operations <NUM>, <NUM>, and <NUM> may be performed in any order depending on the implementation. This is but one example as other flowcharts may be reordered according to a desired implementation.

<FIG> illustrates a block diagram of an example machine <NUM> which may implement one or more of the techniques (e.g., methodologies) discussed herein according to some examples of the present disclosure. Machine <NUM> may implement a user device <NUM>, a remote device <NUM>, a second remote device <NUM>, and the like. For example, the machine <NUM> may be configured to include any one or more of the components of <FIG>, <FIG>, <FIG>, and <FIG>. The machine <NUM> may be configured to perform the methods of <FIG>, <FIG>, and <FIG>. The machine <NUM> may be configured to provide the GUIs of <FIG> and <FIG>. The machine <NUM> may be a user device, a remote device, a second remote device or other device which may take the form of a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a smart phone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine.

Examples, as described herein, may include, or may operate on, logic or a number of components, modules, or mechanisms (hereinafter "modules").

The term "machine readable medium" may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine <NUM> and that cause the machine <NUM> to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting machine readable medium examples may include solid-state memories, and optical and magnetic media. Specific examples of machine readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; Random Access Memory (RAM); Solid State Drives (SSD); and CD-ROM and DVD-ROM disks. In some examples, machine readable media may be non-transitory machine readable media. In some examples, machine readable media may include machine readable media that is not a transitory propagating signal.

Claim 1:
A method for authentication, the method comprising:
using one or more hardware processors:
identifying (<NUM>) a first set of characters corresponding to a stored password;
receiving (<NUM>) a second set of characters to be authenticated during an authentication attempt, wherein the received second set of characters to be authenticated include more characters than the first set of characters corresponding to the stored password; and
causing access to be granted (<NUM>) to an access-controlled resource based upon determining that the second set of characters includes:
a first subset of characters that match the first set of characters (<NUM>) corresponding to the stored password and in a same order, and
a second subset of characters that are not specified for the authentication attempt (<NUM>) and are interleaved with the first subset of characters in an order that is not specified for the authentication attempt, and wherein the characters of said second subset of characters are not part of the first set of characters.