Patent ID: 6986045

Claim:
A method for sending a message, said method comprising the steps of: a) generating by a sender a password P; b) sending the password P to a message recipient over a first channel; c) generating authentication information by the sender for server authentication of the message recipient, wherein the authentication information is dependent on knowing the password P; d) generating by the sender a random number as an initialization vector IV 4 ; e) generating by the sender a private key PK as H(IV 4 |P), where P is a password known to a message recipient, H( ) is an agreed upon hashing algorithm and (|) is a message concatenation; f) generating by the sender an encryption ENC=E(M|H(M), PK), where E is a predetermined symmetric key encryption algorithm, M is the message; g) sending the authentication information and (IV 4 , ENC) from the sender to the server over a second channel; h) authenticating the message recipient over a third channel using the authentication information to verify that the message recipient knows the password P; wherein the authentication information comprises: h-1) the authentication response AR as E(ACNST 2 , ARK) generated by the message recipient, where ACNST 2 is a predetermined constant; h-2) the authentication response key ARK as H(IV 2 |IV 3 |AS), where IV 2 is a second random number (as a second initialization vector) generated by the server and IV 3 is a third random number (as a third initialization vector) generated by the message recipient; h-3) the authentication string AS is as E(ACNST 1 , PK), where ACNST 1 is a predetermined constant and E is a predetermined symmetric key encryption algorithm and AK is an authentication key derived from the password P. i) sending ENC from the server to the message recipient over the third channel only when the message recipient has been authenticated by the server.