# US 8,751,233 B2 · Digital signatures for communications using text-independent speaker verification

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- Number: US 8,751,233 B2
- Document ID: US8751233B2
- Status: Granted
- Kind: B2
- Application number: 13/562,713
- Filed: 2012-07-31
- Published: 2012-11-22
- Granted: 2014-06-10
- Earliest claimed: 2005-12-21
- Assignees: AT&T Intellectual Property II, L.P.
- Applicants: Pradeep K. Bansal; Lee Begeja; Carroll W. Creswell; Jeffrey Farah; Benjamin J. Stern; Jay Wilpon
- Inventors: Pradeep K. Bansal; Lee Begeja; Carroll W. Creswell; Jeffrey Farah; Benjamin J. Stern; Jay Wilpon
- Web page: https://patentgrep.com/patent/US8751233B2

## CPC

- H04L 63/0861: {using biometrical features, e.g. fingerprint, retina-scan (cryptographic mechanisms or cryptographic arrangements for entity authentication using biological data H04L9/3231)}
- G10L 15/02: Feature extraction for speech recognition; Selection of recognition unit
- G10L 17/24: the user being prompted to utter a password or a predefined phrase
- H04L 63/0823: {using certificates (cryptographic mechanisms or cryptographic arrangements for entity authentication involving certificates H04L9/3263)}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

A speaker-verification digital signature system is disclosed that provides greater confidence in communications having digital signatures because a signing party may be prompted to speak a text-phrase that may be different for each digital signature, thus making it difficult for anyone other than the legitimate signing party to provide a valid signature.

## Claims

### Claim 1

A method comprising, performing at an authentication service system:
receiving an authentication session invitation request from a sender of an email, wherein the email is sent to a destination address of a recipient, and wherein the authentication session invitation comprises an email address of the sender and an invitation to create an authentication certificate for the sender and the email;
sending, to the sender, a session identification and a text-phrase prompt comprising a text phrase;
receiving, from the sender in response the text-phrase prompt, the destination address of the recipient and an audio signal;
retrieving, based on the email address of the sender, a voice template associated with the sender;
comparing the audio signal to the voice template, to yield a confidence score;
when the confidence score exceeds a threshold:
generating the authentication certificate; and
packaging the session identification with the authentication certificate, to yield authentication information;
when the confidence score does not exceed the threshold, packaging the session identification and the confidence score as the authentication information; and
transmitting the authentication information to the destination email address of the recipient.

### Claim 2 (depends on 1)

The method of claim 1, wherein the authenticating further comprises:
generating the text phrase; and
transmitting the text phrase to the sender prior to receiving the audio signal from the sender.

### Claim 3 (depends on 1)

The method of claim 1, wherein comparing the audio signal to the voice template further comprises:
performing speech recognition on the audio signal to extract spoken words;
generating a first confidence score by comparing the spoken words against the text phrase;
extracting features from the audio signal;
generating a second confidence score by comparing the features against the voice template; and
combining the first confidence score and the second confidence score to generate the confidence score.

### Claim 4 (depends on 1)

The method of claim 1, wherein the session identification is unique from other sessions with respect to one of: a communication format, a sender system, and the claimed identity.

### Claim 5 (depends on 1)

The method of claim 1, wherein the session identification identifies a type of communication session.

### Claim 6 (depends on 1)

The method of claim 1, wherein the voice template is received from a database.

### Claim 7

A system comprising:
a processor; and
a computer-readable storage medium having instructions stored which, when executed by the processor, cause the processor to perform operations being performed at an authentication service system, the operations comprising:
receiving an authentication session invitation request from a sender of an email, wherein the email is sent to a destination address of a recipient, and wherein the authentication session invitation comprises an email address of the sender and an invitation to create an authentication certificate for the sender and the email;
sending, to the sender, a session identification and a text-phrase prompt comprising a text phrase;
receiving, from the sender in response the text-phrase prompt, the destination address of the recipient and an audio signal;
retrieving, based on the email address of the sender, a voice template associated with the sender;
comparing the audio signal to the voice template, to yield a confidence score;
when the confidence score exceeds a threshold:
generating the authentication certificate; and
packaging the session identification with the authentication certificate, to yield authentication information;
when the confidence score does not exceed the threshold, packaging the session identification and the confidence score as the authentication information; and
transmitting the authentication information to the destination email address of the recipient.

### Claim 8 (depends on 7)

The system of claim 7, wherein the authenticating further comprises:
generating the text phrase; and
transmitting the text phrase to the sender prior to receiving the audio signal from the sender.

### Claim 9 (depends on 7)

The system of claim 7, wherein comparing the audio signal to the voice template further comprises:
performing speech recognition on the audio signal to extract spoken words;
generating a first confidence score by comparing the spoken words against the text phrase;
extracting features from the audio signal;
generating a second confidence score by comparing the features against the voice template; and
combining the first confidence score and the second confidence score to generate the confidence score.

### Claim 10 (depends on 7)

The system of claim 7, wherein the session identification is unique from other sessions with respect to one of: a communication format, a sender system, and the claimed identity.

### Claim 11 (depends on 7)

The system of claim 7, wherein the session identification identifies a type of communication session.

### Claim 12 (depends on 7)

The system of claim 7, wherein the voice template is received from a database.

### Claim 13

A computer-readable storage device having instructions stored which, when executed by a processor of an authentication service system, cause the processor to perform operations comprising:
receiving an authentication session invitation request from a sender of an email, wherein the email is sent to a destination address of a recipient, and wherein the authentication session invitation comprises an email address of the sender and an invitation to create an authentication certificate for the sender and the email;
sending, to the sender, a session identification and a text-phrase prompt comprising a text phrase;
receiving, from the sender in response the text-phrase prompt, the destination address of the recipient and an audio signal;
retrieving, based on the email address of the sender, a voice template associated with the sender;
comparing the audio signal to the voice template, to yield a confidence score;
when the confidence score exceeds a threshold:
generating the authentication certificate; and
packaging the session identification with the authentication certificate, to yield authentication information;
when the confidence score does not exceed the threshold, packaging the session identification and the confidence score as the authentication information; and
transmitting the authentication information to the destination email address of the recipient.

### Claim 14 (depends on 13)

The computer-readable storage device of claim 13, wherein the authenticating further comprises:
generating the text phrase; and
transmitting the text phrase to the sender prior to receiving the audio signal from the sender.

### Claim 15 (depends on 13)

The computer-readable storage device of claim 13, wherein comparing the audio signal to the voice template further comprises:
performing speech recognition on the audio signal to extract spoken words;
generating a first confidence score by comparing the spoken words against the text phrase;
extracting features from the audio signal;
generating a second confidence score by comparing the features against the voice template; and
combining the first confidence score and the second confidence score to generate the confidence score.

### Claim 16 (depends on 13)

The computer-readable storage device of claim 13, wherein the session identification is unique from other sessions with respect to one of: a communication format, a sender system, and the claimed identity.

### Claim 17 (depends on 13)

The computer-readable storage device of claim 13, wherein the session identification identifies a type of communication session.