Two way authentication protocol

A method of authenticating a pair of correspondents C,S to permit the exchange of information therebetween, each of said correspondents having a respective private key, e, d and a public key, Qu and Qs derived from a generator element of a group and a respective ones of said private keys e,d, said method comprising the steps of:

• i. a first of said correspondents C generating a session value x;
• ii. said first correspondent generating a private value t, a said generator and a shared secret value derived from said private value t and said public key Qs of said second correspondent;
• iii. said second correspondent generating a challenge value y and transmitting said challenge value y to said first correspondent;
• iv. said first correspondent in response thereto transmitting said challenge value y, said session value x, and said public value of said first correspondent;
• and
• said second correspondent verifying a corresponding stored identity to thereby verify said first correspondent.

A method of authenticating a pair of correspondents C,S to permit exchange of information therebetween, each of said correspondents C,S having a respective private key e,d and a public key Qu and Qs derived from a generator P and a respective ones of said private keys e,d, a second of said correspondents including a memory for storing public keys of one or more of said first correspondents, said memory including a list of said first correspondents having a unique identification information IDu stored therein, said method comprising the steps of:

• a) said second of said correspondents generating a random value y upon initiation of a transaction between said correspondents;
• b) said second correspondent S forwarding to said first correspondent C said value y;
• c) said first correspondent C generating a first random number x and computing a public session key tP from a private key t,
• d) said first correspondent C generating a message H by combining said first random number x, said value y, said public session key tP and said unique identification information IDu, and computing a signature Se of said message H;
• e) said first correspondent C transmitting said signature Se, said public session key tP, said value x and said identification IDu to said second correspondent;
• f) said second correspondent upon receipt of said message from said previous step (Q) retrieving said public key Qu of said first correspondent from said memory using said received identification information IDu;
• and
• g) said second correspondent verifying said received signature using said recovered public key Qu and verifying said message H and computing a shared secret key d(tP), whereby both said correspondents may calculate a shared secret key k by combining the computed secret tQs=d(tP) with said first random number x and said random value y, said key k being utilized in subsequent transactions between said correspondents for a duration of said session.