Abstract: A system and method for implementing adaptive cryptographically synchronized authentication is disclosed. The authentication system includes a controller that dynamically selects one of a plurality of authentication mechanisms to be used in providing authentication for an exchange of message data. The variation in the level of authentication assurance can be based on one or more factors such as the current security conditions and the available CPU utilization.

Abstract: A high-speed, low-strength authentication mechanism is disclosed. This mechanism is based on a partial message authentication code, wherein a message authentication code is applied only to some portion of the message. By applying an authentication algorithm only to selected parts of the message, significant time can be saved while maintaining acceptable security.

Abstract: Cryptographic keys for a cryptographic function are notarized by encrypting the keys with the cryptographic function using a notarizing cryptographic key derived from identifier designations associated with the encryptor and intended decryptor, respectively, and an interchange key which is accessible only to authorized users of the cryptographic function. Preferably, the identity of a user of the cryptographic function is authenticated as a condition to access to an interchange key. Advantageously, authentication is accomplished by comparing a password designation supplied by the user with a prestored version thereof which has been notarized by having been encrypted with the cryptograpic function using a notarizing cryptographic key derived from the identifier designation of the corresponding authorized user and an interchange key. Signature properties similar to those provided by public key systems are provided for nonpublic keys by allowing a user to use a key for only encryption or decryption and not both.