Method for identification of a user's unique identifier without storing the identifier at the identification site

A method for identification among at least first and second users communicating by means of a communication system, said method comprising the steps of:

• providing a first unique identifier from said first user to said second user,
• entering into an agreement between the various parties as to a first plurality of hash salts;
• at said second user, performing a hash operation on one of (a) said first unique identifier and (b) a deterministic transformation of said first unique identifier, using the first sale from said plurality of salts, to thereby produce a first data hash (A);
• at said second user, performing a hash operation on at least a portion of said first data hash (A) using the second of said plurality of hash salts (B), to thereby produce a second data hash (B);
• at said second user, performing a hash operation on at least a portion of said first data hash (A) using the third of said plurality of hash salts (C), to thereby produce a third data hash (C);
• at said second user, performing a hash operation on at least a portion of said third data hash (C) using the fourth of said plurality of hash salts (D), to thereby produce a fourth data hash (D);
• at said second user, discarding said third data hash (C);
• at said second user, performing a hash operation, using a fifth one of said plurality of hash salts (E), on at least a portion of one of (a) said first unique identifier and (b) data deterministically derived from said unique identifier, to thereby produce a fifth data hash (E);
• at said second user, storing said second and fourth data hashes in memory at locations established by said fifth data hash;
• at said first user, performing a hash operation on at least a portion of one of (a) said first unique identifier and (b) data deterministically derived from said unique identifier, using said fifth data hash, to thereby produce a replica of said fifth data hash;
• transmitting said replica of said fifth data hash from said first user to said second user;
• at said second user, accessing said memory at locations established by said replica of said fifth data hash to obtain said second and fourth data hashes;
• at said second user, generating a random number;
• at said second user, encrypting said random number with a key which includes one of (a) said second data hash and (b) a deterministic transformation of said second data hash, to produce an encrypted random number, where said transformation is agreed to ahead of time;
• at said first user, decrypting said encrypted random number using as a key using one of (a) said second data hash and (b) a deterministic transformation of said second data hash, to extract said random number, to thereby form an extracted random number;
• transmitting from said first user to said second user both said extracted random number and said third data hash;
• at said second user, performing a hash operation on said third data hash by the use of said fourth salt, to thereby generate a sixth data hash (F);
• at said second user, comparing said fourth and sixth data hashes, and deeming said message to be from said first user if they are identical;
• and
• at said second user, discarding said third data hash.