Method of bilateral identity authentication

A method of establishing a session key used to encipher communications between a first party and a second party, said method comprising:

• generating a first exchanged value by said first party;
• generating a first message containing said first exchanged value by said first party;
• enciphering said first message by said first party;
• transmitting said enciphered first message from said first party to said second party;
• deciphering said first message by said second party to recover said first exchanged value;
• generating a second exchanged value by a second party;
• generating a second message containing said second exchanged value by said second party;
• enciphering said second message by said second party;
• transmitting said enciphered second message from said second party to said first party;
• deciphering said enciphered second message by said first party to recover said second exchanged value;
• computing a first key value by said first and second parties;
• computing a second key value by said first and second parties using a symmetrical function with interchangeable arguments, wherein said first and second exchanged values are used as said arguments to compute said second key value;
• and
• combining said first and second key values by said first and second parties to obtain said session key.

A method of establishing a session key used for enciphering communications between a first party and a second party and for authenticating the identities of said first and second parties, said method comprising:

• generating a first authentication challenge by said first party based on a first exchanged value;
• enciphering said first authentication challenge by said first party to a secret key used by said second party;
• transmitting said enciphered first authentication challenge from said first party to said second party;
• deciphering said enciphered first authentication challenge by said second party;
• determining said first exchanged value by said second party;
• generating a second authentication challenge by said second party based on a second exchanged value;
• computing said session key by said second party based on said first and second exchanged value;
• generating a first authentication response by said second party based on said first authentication challenge, wherein said first authentication response contains one or more unpredictable bits;
• transmitting said first authentication response to said first party;
• enciphering said second authentication challenge by said second party to a secret key used by said first party;
• transmitting said enciphered authentication challenge from said second party to said first party;
• receiving said first authentication response and said enciphered second authentication challenge by said first party;
• deciphering said enciphered second authentication challenge by said first party using said secret key;
• determining said second exchanged value by said first party;
• computing said session key by said first party based on said first and second exchanged values;
• and
• authenticating said second party by said first party based on said first authentication response.

A cryptographic communication apparatus used by a first party to communicate with a second party, said apparatus comprising:

• a communications interface for communicating with said second party over a communication channel;
• a processor coupled to said communication interface to perform cryptographic calculations, said processor programmed to:
• generate a first authentication challenge based on a first exchanged value;
• encipher said first authentication challenge to a key used by said second party;
• compute a session key based on said first exchanged value and a second exchanged value received from said second party;
• and
• verify the identity of said second party based on a first authentication response received from said second party.

A cryptographic communication system used for communications between first and second parties, said communication system comprising:

• a first communication terminal connected to a communications channel, said first communications terminal comprising a processor programmed to:
• generate a first authentication challenge containing at least a first exchanged value;
• encipher said first authentication challenge to a key used by said second party;
• decipher a second authentication challenge received from said second party to obtain a second exchanged value;
• compute a session key based on said first exchanged value and said second exchanged value;
• verify the identity of said second party based on a first authentication response received from said second party;
• and
• compute a second authentication response based on said second authentication challenge;
• a second communications terminal connected to said communications channel, said second communications terminal comprising a processor programmed to:
• generate said second authentication challenge containing at least said second exchanged value;
• decipher said first authentication challenge received from said first party to obtain said first exchanged value;
• compute a first authentication response based on said first authentication challenge;
• encipher said second authentication challenge to a key used by said first party;
• compute a session key based on said first exchanged value and said second exchanged value;
• and
• verify the identity of said first party based on a second authentication response received from said first party.