An encryption method is disclosed, including two passes over a sequence of N input digital data X1, . . . XN blocks where the first pass executes iterative linear algebraic operations from the last input block XN to the first input block X1 to obtain a sequence of intermediary resulting YN . . . Y1 blocks. The second pass executes a block ciphering in a chaining mode from the first intermediary resulting Y1 block to the last one YN to obtain a sequence of encrypted output Z1 . . . ZN blocks. The decryption is carried out only in one pass from the first input encrypted Z1 block to the last input encrypted block ZN. The deciphering operations are executed in an iterative loop of inverse linear algebraic operations after deciphering the first input encrypted Z1 block to obtain an output sequence of decrypted X1, . . . XN blocks.