Patent ID: 7702099

Claim:
A symmetric encryption/decryption method, comprising steps of: (A) selecting a diffused mechanism, wherein said diffused mechanism uses a block S k 1 ×k 2 × . . . ×k n as at least one dimensional matrix, and S k 1 ×k 2 × . . . ×k n includes a fixing point and said fixing point is at least one dimensional coordinate, and said coordinate is disposed at (i 1 , i 2 , . . . , i n ), either inside or outside the area of a plaintext A, and moreover, S k 1 ×k 2 × . . . ×k n is placed at a diffused start block, and said diffused start block is used as the center and said plaintext is arranged according to S k 1 ×k 2 × . . . ×k n size, and said block size is used as an unit, such that said diffused start block is used as a center to carry out at least one dimensional diffused operation; (B) retrieving a plurality of bits required for a cipher according to said diffused mechanism and the element numbers of each dimension of a said plaintext; (C) performing a diffused operation A(i 1 , i 2 , . . . , i n ) according to said diffused mechanism in terms of said plurality of bits; and (D) repeating Steps (B) to (C) for a first number of predetermined times so as to convert said plaintext into a ciphertext and achieve effect of encrypting said plaintext.