METHOD TO CODE DATA UNIT REPRESENTED AS BIT STRING Russian patent published in 2015 - IPC G09C1/00 H04L9/00 

FIELD: information technologies.

SUBSTANCE: method to code a data unit represented as a bit string consisting in formation of a secret key in the form of subkeys K and Q, which represent bit strings, formation of an auxiliary n-bit string T, formation of an n-bit auxiliary cryptogram C_M by performance of operation of E coding on the data unit M depending on K according to the formula C_M=E_K(M), formation of an n-bit auxiliary cryptogram C_T by performance of operation of E coding on the n-bit string T depending on Q according to the formula C_T=E_Q(T), formation of 2n-bit cryptogram C depending on subkeys K and Q and auxiliary cryptograms C_M and C_T, differing by the fact that the subkey K is formed as a 2n-bit string, representing concatenation o two n-bit strings k₁ and k₂, the subkey Q is formed as a 2n-bit string, representing concatenation of two n-bit strings q₁ and q₂, the (n+1)-bit string m is formed, and the 2n-bit cryptogram C is formed as concatenation of two binary polynomials of degree n-1, being the solution to the system of two linear equations k₁C₁+k₂C₂=C_M mod m and q₁C₁+q₂C₂=C_T mod m with two unknown binary polynomials C₁ and C₂, in which m is an additionally formed polynomial of degree n, and n-bit strings k₁, k₂, q₁, q₂, C_M, C_T are considered as binary polynomials of degree n-1, and (n+1)-bit string m is considered as a binary polynomial of degree n.

EFFECT: increased level of protection of coded information.

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