CRYPTOGRAPHIC TRANSFORMATION METHOD Russian patent published in 2015 - IPC H04L9/06 

FIELD: physics, computer engineering.

SUBSTANCE: invention relates to cryptography and information security means. A method for cryptographic transformation of a message presented in binary form, which includes calculating, based on an available set of iteration keys K₀, …, K_n, a new set of iteration keys KZ₀, …, KZ_n, wherein the zero key in the new set is determined by the formula KZ₀=K₀ and the remaining keys are determined by the formula KZ_j=L^-1(K_j); calculating binary vectors u[i][j] with length w using the formula u[i][j]=π^-1(τ(j))·G_i; calculating a binary vector m with length w, using the new iteration keys KZ₀, …, KZ_n, performing the following: calculating m_n=S(c), wherein S:V_w→V_w, a=a_t-1|…||a₀, where a_i∈V_b; S(a)=S(a_t-1||…||a₀)=π(a_t-1)||…||π(a₀); calculating $$q_j=\underset{i=0\dots t-1}{\oplus }u\left[i\right]\left[{\tau }^{-1}(m_j\left[i\right])\right];$$ m_j-1=X[KZ_j](q_j), where m_j=m_j[t-1]||m_j[t-2]||…||m_j[0]; j=n, …, 1; X[KZ] is linear transformation which depends on the iteration key KZ, wherein X[KZ]:V_w→V_w, X[KZ](a)=KZ⊕a, where KZ, a∈V_w; calculating m=X[KZ₀](S^-1(m₀)).

EFFECT: faster information processing and fewer operations when performing iterative cryptographic transformation.