The computer-aided method for exchanging encryption key between the network computer unit N and user computer unit U

摘要

(57) [summary] The present invention relates to how to replace the encryption key. Length of the message to be transmitted is reduced, the security properties of the method is significantly expanded than the known methods, according to this. In the user computer unit and the network computer unit, intermediate key and the second intermediate key is generated for the first in dependence on the random number that has been issued. By exclusive OR-bit-by-bit and the intermediate key and the second key intermediate of these first, the session key is calculated. This key is not transmitted in the clear absolutely. For example by using a predetermined function that can be symmetric encryption function, a one-way hash function or user computer unit and the network computer unit with each other are mutually authenticated.