Patent ID: 6064741
Filing Date: 2000-05-16
Classification: H04L

Abstract:
A method for computer-aided exchange of cryptographic keys between a user computer unit and a network computer unit comprising the steps of:generating a first random number;calculating, using the first random number, a first value with a generating element of a finite group in the network computer unit;forming a first message, which has at least the first value, in the network computer unit;transmitting the first message by the network computer unit to the user computer unit;generating a second random number in the user computer unit;forming, using the second random number, a second value with a generating element of a finite group in the user computer unit;calculating a first interim key in the user computer unit by raising a public network key to a power of the second random number;calculating a first encoded term in the user computer unit by encoding an identity indication of the user computer unit with the first interim key using a cryptographic function;calculating a second interim key in the user computer unit by the first value being raised to a power of a secret user key;calculating a session key in the user computer unit by an operation on the first interim key with the second interim key;forming a second message, which has at least the second value and at least the first encoded term, in the user computer unit;transmitting a second message by the user computer unit to the network computer unit;calculating the first interim key in the network computer unit by the second value being raised to a power of a secret network key;calculating the second interim key in the network computer unit in that a public user key is raised to a power of the first random number;calculating the session key in the network computer unit by operation on the first interim key with the second interim key;decoding the first encoded term in the network computer unit; andchecking the identity indication of the user computer unit in the network computer unit.