Patent ID: 7352860

Claim:
A method of enciphering information constituted by a finite sequence {S 1 ,S 2 , . . . ,S N } of N symbols {S 1 ,S 2 , . . . ,S N } selected from an alphabet A, wherein there are defined both a secret convention (K) of p key symbols K 1 , . . . ,K p selected from a second alphabet B, and a multivariate function M having m+1 variables (m<=N): M(X i1 , . . . ,X im ,Y) operating A m ×B in A, {i 1 , . . . , i m } being m distinct indices in the range [1 ,N] and the function M being bijective relative to at least one (X i1 ) of the m variables of A, said enciphering method comprising: initially placing the N symbols S 1 ,S 2 , . . . ,S N ) constituting the information to be enciphered in the N positions of a shift register, and then performing a succession of X turns of the shift register implementing a succession of X permutations on the sequences {S 1 ,S 2 , . . . ,S N } such that where {S 1 ,S 2 , . . . ,S N } is the sequence prior to the j th permutation, the sequence after the j th permutation is {S 2 ,S 3 , . . . ,S N ,Zj}, where Zj is equal to M(S i1 , . . . ,S im ,K j ), the enciphered information being constituted by the sequence {S′ 1 ,S′ 2 , . . . ,S′ N } contained in the shift register at the end of the X th permutation resulting from the X th turn of the shift registers, wherein the number X of permutations is greater than several times the length N of the sequences {S 1 ,S 2 , . . . ,S N }, wherein the number m is equal to 3, the function M being defined by M(X 1 ,X 2 ,X N ,Y), and wherein the function M(X 1 ,X 2 ,X N ,Y) is calculated using the following steps: U=t 1( X 1 ,X N ) V=t 2( U,Y ) Z=t 1( V,X 2 ) t 1 and t 2 being the functions associated with two Latin squares T 1 and T 2 of size equal to the number N.