METHOD OF FORMING AND CHECKING ELECTRONIC TEXT MESSAGE CERTIFIED WITH DIGITAL WATER-MARK Russian patent published in 2009 - IPC H04L9/00 

FIELD: information technologies.

SUBSTANCE: method consists in the fact that there preliminarily formed for a sender and an addressee is a binary sequence of common secret key and hashing function with binary output value; minimum allowable K_min number of original groups of binary sequences of an electronic message from K received groups is set; K≥K_min groups of binary sequences are extracted from the binary sequence of electronic message; electronic message is certified by the sender with digital water-mark by means of pre-formed hashing function and binary sequence of secret key, and the message is transmitted to the addressee; authenticity of the electronic message received with the addressee is checked by means of pre-formed functions of hashing and binary sequence of secret key; in addition, as an electronic message there used is an electronic text message, each symbol of which is represented in the form of its specified binary sequence, and besides there formed is secret key of the sender, which consists of the first, the second, the third and the fourth binary sequences, as well as secret key of the addressee, which consists of the first, the second and the third binary sequences. The proposed method can be used for identifying authenticity of electronic text messages transmitted in modern information telecommunication systems.

EFFECT: increasing protection of the message certified with digital water-mark of the sender against intentional actions of external breakers or potential internal breakers as per the change of its content.

6 cl, 9 dwg