UA18443U - Method of the cryptographic transformation of information - Google Patents

Abstract

The proposed method of the cryptographic transformation of information consists in presenting the information as 128-bit data blocks and performing the iterative processing of the data blocks by simple operations of cryptographic transformation, such as operations of mixing columns, substitution, cyclical shift, and modulo 2 addition. For performing the substitution operation, a substitution matrix is used that is generated by inverting elements g(x) of the finite set GF(28) and using the affinetransformation y = Mx-1 + ? of elements of the finite set GF(2). As the elements g(x), polynomials are used that are selected according to the values of the cryptographic key.

Description

Description of the invention

The proposed useful model refers to the field of cryptographic protection of information and can be used in encryption tools in information processing systems to expand their capabilities.

There is a known method of cryptographic transformation ||, which is based on the fact that the information sequence is presented in the form of 64-bit blocks, which are subject to iterative processing by primitive cryptographic transformations: permutation (regtiiayop) - using permutation blocks (P-blocks); substitution (zirziyshiop) - with the help of substitution blocks (5-blocks); functional operations of cyclic shift and 10 addition modulo 2 - using appropriate devices. Iterative processing consists in multiple execution of the same groups of transformations, which provide the necessary conditions for stability of cryptographic transformation: scattering (using P-blocks) and mixing (using 5-blocks) of information data.

The disadvantage of this method is that 12 fixed matrix of substitutions acts as a C-block for cryptographic transformation of information, which does not allow to flexibly change parameters of cryptographic processing and dynamically control the process of shuffling information data.

The closest to the proposed technical solution, chosen as a prototype, is an improved method of cryptographic transformation |2), which is based on the fact that the information sequence is presented in the form of 128 bit blocks, which are subject to iterative processing by primitive cryptographic transformations: 20 mixing (those) - with the help of column mixing blocks (MixSoYShtp blocks); substitution (zirziyshiop) - with the help of substitution blocks (5-blocks); functional operations of cyclic shift and addition by modulo 2 - with the help of appropriate devices. Iterative processing consists in multiple execution of the same groups of transformations, which provide the necessary conditions for the stability of cryptographic transformation: scattering (with the help of MixSoYshtp blocks) and shuffling (with the help of 5-blocks) of information data. 29 Substitution in ho, heh X7) - UtU Utee U) is a non-linear byte replacement, which is performed independently for each input byte x-yh o, xi... X7). Substitution matrices, with the help of which Z-blocks are constructed, are invertible matrices formed using the composition of two transformations: o 30 1. Obtaining the multiplicative inverse element x""! over the extended finite field Galu a SK(29), " which is constructed by a ring of polynomials with operations modulo an irreducible polynomial " du-khvah hih; (1)

At the same time, it is assumed that if х-0, then х"-0. со 35 2. Performing an affine transformation over the primitive binary field Galu a og(2), which is given by the expression: "- у-М.х7 В, (2) where M is a fixed matrix of the eighth order, symmetric with respect to the auxiliary diagonal: ше: в: ше Ше ШКТ " " ЕВ ВИЕ with с and Ящ У and as ЖоООКИ ой оте . Y , g I t she i

Oh, I'm V

M. t shi SHY NEK y - nenishi i so Shi shk SHE SHE SHK U NE, » VO i i i chiv - ' si ih mn ni niny ss NN NN NI TI s» V - eight-bit column vector: v- 11000119 ".

The disadvantage of this method is that for the cryptographic transformation of information as a Z-block, a fixed matrix of substitutions is used, which is given by obtaining the multiplicative inverse element x 7 over the extended finite Galois field CE(23) modulo a fixed irreducible polynomial (1), which does not allows you to flexibly change the parameters of cryptographic processing and dynamically control the process of mixing information data. 60 The basis of a useful model is the task of creating a method of cryptographic transformation of information, which is due to the use as a 5-block of dynamically changing matrices of substitutions, which are given by obtaining multiplicatively inverse elements of x"" over extended finite Galois fields OE(2 8). modulo variable irreducible polynomials d(x), which are chosen according to the value of the cyclic key.

The technical result that can be obtained when implementing a useful model consists in obtaining the ability to flexibly change the parameters of cryptographic processing and dynamically manage the process of mixing information data.

The essence of the proposed method of cryptographic transformation of information is that the information sequence is presented in the form of 128-bit blocks, which are subject to iterative processing by primitive cryptographic transformations: mixing (those) - with the help of column mixing blocks (MixSoYShtp blocks); substitution (zirziyshiop) - using substitution blocks (5-blocks); functional operations of cyclic shift and addition by modulo 2 - with the help of appropriate devices. As a 5-block, there is a variable matrix of substitutions, which is constructed by obtaining the multiplicative inverse element x"! over the extended finite Galois field OE(29) with operations modulo the irreducible polynomial d(x) and by performing the affine transformation (1) over the primitive binary field Galois CE (2), while variable polynomials are used as the 70 irreducible polynomial d(x), which are chosen according to the value of the cyclic key.

The cyclic key is generated from the encryption key using a key generation algorithm. The length of the cyclic key is equal to the length of the block. Cycle keys are generated from the encryption key using key expansion. The extended key is a linear array of 4-byte words. That is, at each iteration 75 of the cryptographic transformation, variable irreducible polynomials d(x) are used to form the 5-block, which can be chosen from the 4-byte words of the extended key in an arbitrary way, for example, by using the first byte of the cyclic key. This makes it possible to flexibly change the substitution matrix in the process of cryptographic transformation and, accordingly, to dynamically control the process of shuffling information data.

Replacing the irreducible polynomial d(x) leads to an isomorphic mapping of the elements of the extended finite Galois field B(2 89). The main indicator of the effectiveness of the substitution blocks - the indicator of the nonlinearity of the cryptographic transformation is invariant to the isomorphic mapping. Therefore, the non-linearity index of the transformation performed using the formed C-blocks is equal to the non-linearity index in the prototype method. Therefore, the proposed technical solution allows performing cryptographic transformation of data by flexibly changing substitution tables with a fixed nonlinearity index and dynamically controlling iterative processing of information data. with

Thus, due to the use of variable irreducible polynomials d(x), it is possible to use dynamically changing substitution matrices as a C-block at each iteration of the cryptographic transformation of information, which makes it possible to flexibly change the parameters of cryptographic processing and dynamically control the process of shuffling information data. co

Sources of information: « 1. Myopia! Ipziyshe oi BZ(apdagaz apa Tesppoiodu, "BIRBZ-46-3: Yuaya Eepsguriop BZ(apdaga" Osi. 1999,

Amayarieye ai per://svgs.pivi dom/rybiisayopelLirv/ pEr://svgo.tvi.dom/rybiisayopeLreyirz46-ZLirz46-3. paradise « 2. Myope! Ipviyshsche oi 5(apdagaz apa Tesppoiodu, "RIRB-197: Admapsedi Epsguriop Ziapdaga Mom. 2001. so

Aumayariye ai trans:/svgs.pivy. dom/rybiisayopelLrv/ pEer://svgo.pivi dom/rybiisayopelLirelirv 197Lirv-197.raye ch-

Claims (1)

The formula of the invention is the method of cryptographic transformation of information, which consists in the fact that the information sequence is presented in the form of 128-bit blocks, which are subject to iterative processing by primitive cryptographic transformations: mixing (those) - using column mixing blocks (MixSoYshtp blocks); substitution and (zirziyshiop) - using blocks of substitutions (5-blocks); functional operations of cyclic shift and "» addition modulo 2 - with the help of appropriate devices, which is distinguished by the fact that as a 5-block there is a variable matrix of substitutions, which are constructed by obtaining a multiplicative inverse element x 7 over the extended finite Galois field CE(23) with operations modulo the irreducible polynomial d(x) and by performing the affine transformation y-Mech 7-8 over the primitive Galois binary field OK(2), while as (oo) the irreducible polynomial d(x) variable polynomials are used, which are chosen according to the value of their cyclic key. ч 20 Official Bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated microcircuits", 2006, M 11, 11/15/2006. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. with 60 b5