Importance

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Abstract

A system which employs a pair of encryption functions f and g in the 'log on' protocol of a computer dial-up arrangement. The functions are inverses of each other and, hence, a random sequence when encrypted with f and then with g results in the original sequence. When a user wishes to 'log on', the computer selects a random sequence and forms a challenge sequence. The user encrypts the challenge sequence with the function g and thus forms a response sequence. Encryption with the function f by the computer permits verification of the response sequence. The secrecy of the user's function is maintained by providing the user with an authenticating device having only two ports: a power port and an I/O port. The I/O port is connected to a microprocessor which accesses a memory that contains the secret encryption function g.

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First Claim