The invention provides a cryptographic method which includes receiving at a first entity a second public key M.sub.A. At least one of a first session key K.sub.B and a first secret S.sub.B may be generated based on the second public key M.sub.A. A first random nonce N.sub.B may be generated which may be encrypted with at least one of the first session key K.sub.B and the first secret S.sub.B to obtain an encrypted random nonce. The encrypted random nonce may be transmitted from the first entity. In response to transmitting the encrypted random nonce, the first computer may receive a data signal containing a modification of the first random nonce N.sub.B+1. If the modification of the first random nonce N.sub.B+1 was correctly performed, then at least one of (i) opening a communication link at the first computer, and (ii) generating a first initialization vector I.sub.B is performed.