Identity and content authentication for phone calls

1. A method for call authentication comprising:

an enrollment protocol that ensures a user controls a number the user claims to own;

a handshake protocol that mutually authenticates two calling parties comprising a caller and a callee; and

a call integrity protocol that ensures the security of a voice channel and a content it carries, wherein the call integrity protocol comprises:

sending a message indicating that a voice call is connected, wherein the message comprises a timestamp and a hash message authentication code (HMAC) of the timestamp by the caller and the callee;

sending other audio digests by the caller and the callee after the voice call begins; and

sending a call concluded message comprising a timestamp with an HMAC.

2. The method according to claim 1 , wherein a server acts as either an endpoint or intermediary between user clients.

3. The method according to claim 1 , wherein all of the protocols implement end-to-end cryptography.

4. The method according to claim 1 , wherein the enrollment protocol issues a certificate that binds an identity of the client to a phone number.

5. The method according to claim 4 , wherein the enrollment protocol comprises:

establishing a client C and an enrollment server S;

(message 1) C sending an enrollment request with S's identity, C's identity information, C's phone number, and C's public key;

(message 2) S sending a nonce N Net , the identities of C and S and the phone numbers of C and S with a timestamp to ensure freshness, liveness, and to provide a “token” for the particular authentication session;

(message 3) S confirming that C controls the phone number it claims by S placing a call to C's claimed phone number, and S transmitting a nonce N Audio over the voice channel when a call is answered;

(message 4) C sending both the nonce N Net and the nonce N Audio along with the IDs of server, client, a timestamp, and a signature covering all other fields; and

(message 5) S replying with a signed certificate issued to C.

6. The method according to claim 5 , wherein the enrollment protocol comprises an out-of-band process for verifying identity of certificates (particularly high-value certificates), authentication of supporting documentation, and/or CNAM3 lookups.

7. The method according to claim 1 , wherein the handshake protocol comprises a first phase indicating to a server and the two calling parties that a call is imminent and a second phase of authenticating both parties on the call and establishing shared secrets.

8. The method according to claim 1 , wherein the other audio digests are transmitted for a duration of the voice call and are authenticated with HMACs.

9. A method of authentication, comprising:

performing an enrollment protocol between a client and a server to ensure that a user controls a phone number and to issue a certificate to the user;

performing a handshake protocol between two calling parties comprising a caller and a callee through the server to authenticate the two calling parties; and

performing a call integrity protocol to ensure security of a voice channel and a content it carries, wherein the call integrity protocol comprises:

sending a message indicating that a voice call is connected, wherein the message comprises a timestamp and a hash message authentication code (HMAC) of the timestamp by the caller and the callee;

sending other audio digests by the caller and the callee after the voice call begins; and

sending a call concluded message comprising a timestamp with an HMAC.

10. The method according to claim 9 , wherein the certificate the enrollment protocol binds an identity of the client to the phone number.

11. The method according to claim 10 , wherein the identity comprises at least one of a name, an organization, and pertinent information.

12. The method according to claim 11 , wherein the enrollment protocol comprises:

sending an enrollment request with the server's identity, the client's identity, the client's phone number, and the client's public key by the client;

sending a nonce N Net , the identities of the client and the server, and the phone numbers of the client and the server with a timestamp by the server;

sending the nonce N Net and an audio nonce N Audio by the client; and

replying with a signed certificate issued to the client by the server.

13. The method according to claim 12 , wherein the server provides a token during sending the nonce N Net .

14. The method according to claim 9 , wherein the handshake protocol comprises a first phase indicating imminent call between the server and the calling parties, and a second phase authenticating the calling parties.

15. The method according to claim 14 , wherein the first phase comprises:

indicating by the caller to the server that the caller wants to place a call;

informing by the server to the callee that an authenticated voice call is coming; and

informing by the server to the caller whether the callee is using the authenticated voice call.

16. The method according to claim 15 , wherein the caller and the callee compute independently messages and send the messages in parallel during the second phase of the handshake protocol.

17. The method according to claim 16 , wherein the messages contain all information necessary for a Diffie-Hellman Key establishment authenticated with a signature key in a certificate of the caller and the callee.

18. The method according to claim 9 , wherein the call integrity protocol confirms that the voice channel is established and confirms when a call ends.

19. A method of authentication, comprising:

performing an enrollment protocol between a client and a server to ensure that a user controls a phone number and to issue a certificate to the user;

performing a handshake protocol between two calling parties comprising a caller and a callee through the server to authenticate the two calling parties; and

performing a call integrity protocol to ensure security of a voice channel and a content it carries,

wherein the enrollment protocol comprises:

sending an enrollment request with the server's identity, the client's identity information, the client's phone number, and the client's public key by the client;

sending a nonce N Net , the identities of the client and the server, and the phone numbers of the client and the server with a timestamp by the server;

sending the nonce N Net and an audio nonce N Audio by the client; and

replying with a signed certificate issued to the client by the server, wherein the handshake protocol comprises:

indicating by the caller to the server that the caller wants to place a call;

informing by the server to the callee that an authenticated voice call is coming; and

informing by the server to the caller whether the callee is using the authenticated voice call, and

wherein the call integrity protocol comprises:

sending a message indicating that a voice call is connected, wherein the message comprises a timestamp and a hash message authentication code (HMAC) of the timestamp by the caller and the callee;

sending other audio digests by the caller and the callee after the voice call begins; and

sending a call concluded message comprising a timestamp with an HMAC.