Abstract:
A method and an apparatus are disclosed that enable an enhanced, interactive voice response (IVR) system to securely authenticate a user at a telecommunications terminal, without some of the disadvantages in the prior art. In particular, after the user at the telecommunications terminal requests access to a resource, the controlling IVR system of the illustrative embodiment issues a random challenge sequence to the user, along with interspersed “camouflage elements” and one or more directions as to how to respond. The user is then free to speak a returned sequence that answers the combined challenge sequence and interspersed camouflage elements; as a result, an eavesdropper overhearing the user hears what sounds like a random number or string. In short, the technique of the illustrative embodiment uses a challenge-response exchange of a substitution cipher interspersed with camouflage elements.

Description:
FIELD OF THE INVENTION 
     The present invention relates to telecommunications in general, and, more particularly, to a secure method of authenticating a user from a telecommunications terminal by using voiced responses from the user. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  depicts telecommunications system  100  in accordance with the prior art. Telecommunications system  100  comprises telecommunications network  105 , interactive voice response (IVR) system  110 , and database system  115 , interconnected as shown. 
     Telecommunications network  105  is a network such as the Public Switched Telephone Network [PSTN], the Internet, and so forth that transports signals between IVR system  110  and other devices, such as telecommunications terminal  106 . Telecommunications terminal  106  is a device that is capable of handling voice signals from a user, such as a desktop or notebook computer with a microphone/headset combination, a cellular phone, a hands-free messaging system, and so forth. 
     IVR system  110  is a data-processing system that enables a user to log in from a remote telecommunications terminal by accepting a combination of voice input and touch-tone keypad selection from the user, and by providing appropriate responses to the user in the form of voice or other media. The user interacts with IVR system  110  to acquire information from or provide information to associated database server  115 . The user, having an account on database server  115  or on some other data-processing system associated with system  110 , can access one or more resources or services via a telecommunications terminal such as terminal  106  once system  110  grants access to the user. 
       FIG. 2  depicts a signal flow diagram of signals exchanged between terminal  106  and IVR system  110  in accordance with the prior art. In the signal flow, the user of terminal  106  attempts to access a resource that is associated with database server  115 . In response, system  110 , which controls the access to server  115 , performs authentication on the user by using a first technique in the prior art. Authentication is the process by which a security system, such as one that comprises system  110 , verifies that a user is indeed who he or she claims to be. Authentication is a well-understood process in data communications, and many protocols exist in the prior art that provide a level of security through authentication. 
     Terminal  106  transmits, via signal  201 , the user&#39;s identity to IVR system  110 . System  110  then looks up the corresponding personal identification number (or “PIN”) for the user who is “logging in.” 
     IVR system  110  transmits, via signal  202 , a prompt for the user of terminal  106  to enter his or her PIN. 
     Terminal  106  transmits, via signal  203 , the PIN information that the user enters via the terminal&#39;s keypad. 
     If the PIN transmitted via signal  203  matches the user&#39;s PIN on record, IVR system  110  grants the user, via signal  204 , access to the requested resource. 
     The disadvantage in using this first authentication technique is that many telecommunications terminals are hands-free devices that are operated by user voice commands—sometimes exclusively by voice commands. If such a terminal&#39;s user speaks a password instead of entering it via a keypad, then eavesdroppers can hear the password, and the security of database server  115  is consequently breached. 
     Other techniques for authenticating a user exist in the prior art. In a second technique in the prior art, the user speaks the password while ensuring that no one can overhear the spoken password. The disadvantage with the second technique is that it is often unreasonable to rely on the user to ensure that no one can overhear. In a third technique in the prior art, the user utilizes an electronic token device or a list of numbers to respond to an authentication request with a one-time password response. The disadvantage with the third technique is that it is inconvenient for the user to carry around the token device or list, and having to carrying around something is anyway inconsistent with the notion of using a hands-free terminal. In a fourth technique in the prior art, the authenticating system performs speaker verification on the person requesting access. The disadvantage with the fourth technique is two-fold: the high error rate of speaker verification and concerns that an eavesdropper can record and, therefore, impersonate the user&#39;s voice make using the speaker verification technique problematic. 
     Therefore, what is needed is a secure authentication technique that is based on voiced user responses, without some of the disadvantages in the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention enables an enhanced, interactive voice response (IVR) system to securely authenticate a user at a telecommunications terminal, without some of the disadvantages in the prior art. In particular, after the user at the telecommunications terminal requests access to a resource, the controlling IVR system of the illustrative embodiment issues a random challenge sequence to the user, along with interspersed “camouflage elements” and one or more directions as to how to respond. The illustrative embodiment takes advantage of an eavesdropper not being able to hear the challenge sequence because the user is listening to the IVR system in private on a receiving device, such as headset or telephone handset. The user is then free to speak a returned sequence that answers the combined challenge sequence and interspersed camouflage elements; as a result, an eavesdropper overhearing the user hears what sounds like a random number or string. In short, the technique of the illustrative embodiment uses a challenge-response exchange of a substitution cipher interspersed with camouflage elements. 
     In a first example of the disclosed technique, instead of memorizing a single N-digit personal identification number, such as “4296”, the user memorizes N randomly generated substitutions, such as “Red equals 4,” “Green equals 2,” “Blue equals 9,” and “Yellow equals 6.” The challenge sequence can be in any order or subset of these colors, and the correct response sequence by the user consists of the numeric digits that correspond to the colors. Furthermore, the challenge sequence—for example, “Yellow, Red, Green”—is augmented with interspersed, unencrypted symbols, which are the camouflage elements referred to earlier. For instance, the sequence that is transmitted as voice signals to the user might be “3, Yellow, 0, 5, Red, Green”, which would mean that the correct string returned as voice signals from the user would be “3, 6, 0, 5, 4, 2”. 
     In a second example of the disclosed technique, the user memorizes a single N-digit personal identification number (PIN), such as “4296”. The challenge sequence essentially consists of prompts for the digits in the PIN in random order, and the response sequence by the user consists of the correct digits in response to the prompts. Furthermore, the challenge sequence—for example, “Say the third digit, Say the first digit” and so on—is augmented with interspersed, unencrypted symbols (i.e., the camouflage elements). For instance, the sequence transmitted as voice signals to the user might be “3, Say the fourth PIN digit, 0, 5, Say the second PIN digit, Say the third PIN digit”, and so on. The correct response from the user would then be “3, 6, 0, 5, 2, 9”, and so on. In some alternative embodiments, the prompt for the digits of the PIN might be in a non-random order. 
     In accordance with the illustrative embodiment, the orders of challenge elements and camouflage elements are random as is the interspersion of these two types of elements in the transmitted sequence. The numbers of challenge and camouflage elements are chosen to maximize secrecy and minimize authentication time. To achieve the security levels required and to convey no future authentication information to an eavesdropper, the relationship between the number of challenge elements and the number of camouflage elements is taken into consideration. 
     The illustrative embodiment of the present invention comprises: a transmitter for transmitting, to a user: (i) a first symbol unencrypted, (ii) a first direction to return, unencrypted, the first symbol, (iii) a challenge, and (iv) a second direction to return a response to the challenge; and a receiver for receiving the first symbol and the response from the user; wherein the first symbol and the response are symbols in the same alphabet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts telecommunications system  100  in accordance with the prior art. 
         FIG. 2  depicts a signal flow diagram of signals exchanged between terminal  106  and IVR system  110  in accordance with the prior art. 
         FIG. 3  depicts telecommunications system  300  in accordance with the illustrative embodiment of the present invention. 
         FIG. 4  depicts the salient components of IVR system  310  in accordance with the illustrative embodiment of the present invention. 
         FIG. 5  depicts a flowchart of the salient tasks of IVR system  310  authenticating a user, in accordance with the illustrative embodiment of the present invention. 
         FIG. 6  depicts a signal flow diagram of an authentication procedure in accordance with the illustrative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following terms are defined for use in this Specification, including the appended claims:
         The term “string” is defined as a contiguous sequence of elements (e.g., symbols, etc.) of the same type (e.g., the numeric digits, the letters of the Latin alphabet, etc.). For example, the string {1, 3, 9, 2, 7} consists of elements that are numeric digits.   The term “alphabet” is defined as a system of representative symbols. For example, the alphabet of numeric digits (a first alphabet type) consists of the numbers 0 through 9. The alphabet of the colors of a rainbow (a second alphabet type) consists of the names of the colors red, orange, yellow, green, blue, indigo, and violet. The symbols in an alphabet can be used as elements in a sequence or string.       

       FIG. 3  depicts telecommunications system  300  in accordance with the illustrative embodiment of the present invention. Telecommunications system  300  comprises telecommunications network  105 , which serves telecommunications terminal  106 , and enhanced interactive voice response (IVR) system  310 , interconnected as shown. 
     Enhanced IVR system  310  is an interactive voice response system, as is known in the art, that enables a user to log in from a remote telecommunications terminal such as terminal  106 . System  310  enables the user to log in by accepting voice input (and, in some embodiments, touch-tone keypad selection), and by providing appropriate commands and replies to the user in the form of voice or other media. The user interacts with system  310  to acquire information from or provide information to associated database server  115  through the telecommunications terminal. If system  310  grants the user access, the user is then able to use one or more resources or services associated with database server  115 . As those who are skilled in the art will appreciate, in some alternative embodiments, system  310  can authenticate a user on behalf of another data-processing system other than server  115 . 
     In accordance with the illustrative embodiment, enhanced IVR system  310  securely authenticates each user who logs in, as described below and with respect to  FIGS. 5 and 6 . In support of secure authentication, system  310  is capable of transmitting voice signals to a user and is capable of receiving voice signals from a user, in well-known fashion. As those who are skilled in the art will appreciate, in some alternative embodiments, a data-processing system other than an interactive voice response system can be used to authenticate the user. In any case, it will be clear to those skilled in the art, after reading this specification, how to make and use enhanced IVR system  310 . 
       FIG. 4  depicts the salient components of enhanced IVR system  310  in accordance with the illustrative embodiment of the present invention. System  310  comprises receiver  401 , processor  402 , memory  403 , transmitter  404 , and clock  405 , interconnected as shown. 
     Receiver  401  receives (i) signals from telecommunications terminals such as terminal  106  via telecommunications network  105  and (ii) signals from database server  115 , and forwards the information encoded in the signals to processor  402 , in well-known fashion. It will be clear to those skilled in the art, after reading this specification, how to make and use receiver  401 . 
     Processor  402  is a general-purpose processor that is capable of receiving information from receiver  401 , executing instructions stored in memory  403 , reading data from and writing data into memory  403 , executing the tasks described below and with respect to  FIG. 5 , and transmitting information to transmitter  404 . In some alternative embodiments of the present invention, processor  402  might be a special-purpose processor. In either case, it will be clear to those skilled in the art, after reading this specification, how to make and use processor  402 . 
     Memory  403  stores the instructions and data used by processor  402 . Memory  403  might be any combination of random-access memory (RAM), flash memory, disk drive memory, and so forth. It will be clear to those skilled in the art, after reading this specification, how to make and use memory  403 . 
     Transmitter  404  receives information from processor  402  and transmits signals that encode this information to (i) telecommunications terminals such as terminal  106  via telecommunications network  105  and (ii) database server  115 , in well-known fashion. It will be clear to those skilled in the art, after reading this specification, how to make and use transmitter  404 . 
     Clock  405  transmits the current time and date to processor  402  in well-known fashion. 
       FIG. 5  depicts a flowchart of the salient tasks of enhanced IVR system  310  authenticating a user, in accordance with the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted  FIG. 5  can be performed simultaneously or in a different order than that depicted. 
     When a user account is initialized or changed, at task  501 , enhanced IVR system  310  shares N randomly generated substitution symbols with a user, wherein N is a positive integer. These symbols correspond to a secret string of symbols that is known only to the user and the security system. For example, if the secret string is “4296” (i.e., N is equal to four), then system  310  might have the user memorize “red=4, green=2, blue=9, yellow=6”, wherein the substitution symbols “red,” “green,” “blue,” and “yellow” are from an alphabet whose type is the names of colors. In some alternative embodiments, the secret string of symbols is used as a password, such as a personal identification number (or “PIN”), in which case system  310  does not require that the new user memorize substitution symbols. As those who are skilled in the art will appreciate, many methods exist that provide adequate security in the sharing of the information with the user, such as a letter or email with minimal details that is sent to the user&#39;s address of record. 
     Later on when the user wishes to access system  310  (e.g., via terminal  106 , etc.), at task  502 , system  310  receives the user&#39;s identity (e.g., a user name, an account number, a calling telephone number, etc.) in well-known fashion. System  310  looks up the secret string of symbols (i.e., “4296”) and the substitutions (i.e., “Red=4, Green=2, Blue=9, Yellow=6”) that are associated with the particular user. 
     At task  503 , system  310  generates one or more authentication challenge elements h 1 , . . . , h M  as part of an authentication challenge sequence H, wherein M is a positive integer less than or equal to N. The challenge elements are based on the user&#39;s memorized substitutions (i.e., Red, Green, Blue, Yellow), in that the challenge elements are in any order or from any subset of the substitutions. For example, a first challenge sequence might be equal to {Yellow, Red, Green}, and a second challenge sequence might be equal to {Blue, Green, Red, Yellow}. 
     System  310  also generates at task  503  one or more camouflage elements f 1 , . . . , f P , wherein P is a positive integer. The symbols that make up the camouflage elements are from the same alphabet (e.g., the set of numeric digits, etc.) as are the elements of the user&#39;s secret string. As those who are skilled in the art will appreciate, the number of camouflage elements are chosen based on the number of challenge elements, so as to achieve the required security levels and to convey no future authentication information to an eavesdropper listening in on the user. In some embodiments, the challenge elements and camouflage elements are chosen so that the returned sequence R to be received from the user comprises, assuming that the user spoke the sequence correctly, at least one instance of every symbol in the alphabet (e.g., the set of numeric digits, etc.) that is used by returned sequence R. For example, if the challenge elements were “yellow, red, green,”which correspond to “6, 4, 2,” then the camouflage elements to be used would be the digits 0, 1, 3, 5, 7, 8, and 9, not necessarily in the order shown. 
     There is, of course, the possibility that an eavesdropper could try to log in as the user to crack the security system. By listening to the obvious differences between challenge elements (e.g., “red”, etc.) and camouflage elements (e.g., “7”, etc.), the eavesdropper might eventually figure out the user&#39;s secret string. To address this possibility, in some embodiments, the number of elements in the overall transmitted sequence of challenge and camouflage elements exceeds the total number of different symbols in the alphabet that is used to represent the user&#39;s secret string. For instance, if the secret string consists of numeric digits, the total number of elements transmitted by system  310  should be at least eleven, in some embodiments. 
     In generating the challenge and camouflage elements, system  310  forms transmitted sequence T, which is made up of challenge elements h 1 , . . . , h M  and camouflage elements f 1 , . . . , f P . In forming transmitted sequence T, system  310  intersperses the camouflage elements of the illustrative embodiment (also referred to as “unencrypted symbols”) among the challenge elements of the illustrative embodiment. The order of the challenge elements and the camouflage elements is random, as is the interspersion of the two types of elements in transmitted sequence T. 
     At task  504 , system  310  transmits to the user the jth element of transmitted sequence T, starting with the first element. System  310  will execute task  504  for each element to be transmitted in sequence T, for j=1 through J wherein J has a value of (M+P). By repeatedly executing task  504 , in accordance with the illustrative embodiment, system  310  transmits to the user voice signals that convey:
         i. one or more unencrypted symbols (i.e., camouflage elements),   ii. one or more challenges (i.e., challenge elements),   iii. at least one direction for the user to return, unencrypted, the one or more unencrypted symbols being transmitted, and   iv. at least one direction for the user to return responses to the one or more challenges.       

     In accordance with the illustrative embodiment, system  310  transmits each element in transmitted sequence T one at a time and waits after each element transmitted for the corresponding element in the returned sequence R to be received. Alternatively, system  310  can transmit the entire transmitted sequence T before expecting the returned sequence R to be received from the user. 
     In transmitting the one or more directions to the user, system  310  provides the user with verbal commands in combination with the unencrypted symbols and challenges. As a first example, system  310  might tell the user something like “Say the number 3, Say the number that stands for ‘Yellow’, Say the number 0”, and so on; in the example, “3” and “0” are some of the unencrypted symbols transmitted, and “Yellow” is one of the challenges transmitted. As a second example, system  310 , might tell the user in advance what do to and then provide the series of challenges and unencrypted symbols to the user. 
     In accordance with the illustrative embodiment, system  310  transmits audio-bearing signals to the user, who receives the information encoded in the signals through a headset. In some alternative embodiments, system  310  transmits video-bearing signals to the user, who receives the information encoded in the signals via the video display on the user&#39;s telecommunications terminal. For example, system  310  can transmit pictures instead of symbols as part of transmitted sequence T (or its equivalent), such as a picture of a dog, then a picture of “1”, then a picture of “4”, then a picture of a flower, and so forth. 
     System  310 , in some alternative embodiments, transmits the unencrypted symbols interspersed with prompts for each digit of the user&#39;s secret string such as a person identification number (or “PIN”). For example, system  310  might tell the user something like “Say the number 3, Say the fourth digit of your PIN, Say the number 0”, and so on; in the example, “3” and “0” are some of the unencrypted symbols transmitted, and “the fourth digit of your PIN” is essentially one of the challenges transmitted. 
     In some embodiments, system  310  regulates the time taken to transmit one or more of the directions to the user; system  310  bases the time taken on an estimate of the time needed by the user to return the responses to the challenges. It is generally easier for the user to repeat an unencrypted symbol that is told to the user than it is for the user to recall and say the correct response to a challenge (e.g., “6” being the correct response to the challenge “Yellow”, etc.); therefore, system  310  might deliberately retard the transmitting of one or more of the unencrypted symbols. System  310  regulates at least some of the transmissions so as not to allow an eavesdropper to figure out which of the voiced returns by the user are the unencrypted symbols (i.e., the elements that are quick to repeat) and which are the responses to the challenges (i.e., the elements that take longer to recall and return). 
     At task  505 , system  310  receives the corresponding jth returned element as part of returned sequence R. The returned element from the user might be either a voiced return of the corresponding unencrypted symbol or a voiced response to the corresponding challenge already transmitted by system  310 . 
     In accordance with the illustrative embodiment, system  310  receives audio-bearing signals from the user, who provides the information encoded in the signals through a microphone. In some alternative embodiments, system  310  receives keypad-originated signals (e.g., dual tone multi-frequency [DTMF] signaling, etc.) from the user, who provides the information encoded in the signals via the keypad on the user&#39;s telecommunications terminal. For example, system  310  might receive returned sequence R via a series of DTMF tones. An embodiment of the present invention that accommodates keypad-originated signals from the user can be applied to provide security in the presence of a “keyboard sniffer” (or “keyboard logger”), which is malware that records a telecommunications terminal&#39;s keystrokes, including typed passwords. 
     At task  506 , system  310  determines if it has transmitted the entire transmit sequence T. If it has, task execution proceeds to task  507 . Otherwise, task execution proceeds back to task  504  to transmit and receive the next transmitted/returned element pair in sequences T and R, respectively. 
     At task  507 , system  310  determines if returned sequence R is correct for the particular user. As those who are skilled in the art will appreciate, various criteria exist for determining whether the sequence is correct, such as matching all of the elements, matching a majority of the elements, and so forth. If returned sequence R is correct, task execution proceeds to task  508 . Otherwise, task execution ends. 
     At task  508 , system  310  grants the requested access to the user. The access, for example, might be to a particular database or to a transaction procedure that involves database server  115 . After task  508 , task execution ends. 
       FIG. 6  depicts a signal flow diagram of an authentication procedure in accordance with the illustrative embodiment of the present invention. In the signal flow, the user of telecommunications terminal  106  is attempting to gain access to a resource, wherein enhanced IVR system  310  controls access to the resource and authenticates the user accordingly. The figure illustrates that the technique of the illustrative embodiment uses a challenge-response exchange of a substitution cipher that is augmented with interspersed camouflage elements, wherein the technique permits the user to reply verbally to the challenge and camouflage elements. For illustrative purposes, the depicted signal flow shows all of the challenge elements and camouflage elements that constitute transmitted sequence T as being transmitted contiguously to the user. 
     Referring to  FIG. 6 , terminal  106  transmits, via signal  601 , its user&#39;s identity and an access request to enhanced IVR system  310  in well-known fashion 
     System  310 , via signal  602 , transmits transmitted sequence T to terminal  106  in accordance with the illustrative embodiment. Transmitted sequence T comprises one or more unencrypted symbols and one or more challenges. System  310  also transmits directions to terminal  106  on how the user should respond. The sequence transmitted via voice signals to the user might be: 
     3, Yellow, 0, 5, Red, Green. 
     Terminal  106  transmits, via signal  603 , returned sequence R to system  310 . Returned sequence R comprises the one or more unencrypted symbols and the one or more responses that correspond to the challenges, assuming that the user replies correctly, where all symbols and responses are in the same alphabet. For the transmitted sequence given above, the correct sequence returned verbally by the user would be: 
     3, 6, 0, 5, 4, 2. 
     Based on a correct returned sequence R, system  310 , via signal  604 , notifies the user that the access request has been granted. 
     It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc. 
     Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.