METHOD OF COMPOSING AND CHECKING ELECTRONIC TEXT MESSAGE AUTHENTICATED BY DIGITAL WATERMARK Russian patent published in 2009 - IPC H04L9/00 

FIELD: physics; communications.

SUBSTANCE: present invention relates to telecommunications and information technology. First and second binary sequences of a secret key are generated and a set of substitute characters is established for characters of the electronic message, which do not change its visual perception. The electronic message is authenticated by the user using a digital watermark using a hashing function and secret key sequences and then sent to a user, where authenticity of the received electronic message is checked using the same functions. K successively received groups of binary sequences of the electronic message are authentic if the number of matches of values calculated from successively received groups of hashing functions reaches K_c≥K_min. The minimum admissible number K_min of authentic groups of binary sequences of the electronic text message from K received groups is determined from the expression , where P_adm - is the pre-set admissible probability of receiving K authentic groups of binary-sequences of an electronic text message, which are not authentic, - is the number of combinations from K to µ, and L is the number of known malefactors of authenticated electronic text messages.

EFFECT: increased integrity of an electronic message.

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