| 摘要 |
<p>A method and a system for encrypting plaintext digital data divided into a sequence (SEQP) comprising N successive blocks (P 1 , P 2 , P 3 ,..., P N ) of a same length of n bits each and a residual plaintext block (PR) having a length of m bits lower than the length of one of the N successive blocks (P 1 , P 2 , P 3 ,..., PN). The N successive plaintext blocks (P 1 , P 2 , P 3 ,..., PN) are ciphered with the main encryption key (K) by using a predefined encryption algorithm to obtain a sequence (SEQC) of N successive ciphered blocks (C 1 , C 2 , C 3 ,....C N ) of the same length than the plaintext blocks (P 1 , P 2 , P 3 ,..., PN). A set of round keys (K 1 , K 2 , K 3 ,...K n ) having a same length are generated by applying a component common to encryption and decryption on the main encryption key (K). The round keys (K 1 , K 2 , K 3 ,...K n ) of the set are combined together to obtain a resulting string (ST) having a length equal to the length of a block of the sequence (SEQP). The residual plaintext block (PR) is then combined with the most left bits of the resulting string (ST) forming a string (T) having a length equal to the length of the residual block (PR) to obtain a residual ciphered block (CR). The method and the system apply also to decipher a sequence of N successive ciphered blocks followed by a ciphered residual block and may also use a ciphering or deciphering algorithm based on a CBC mode.</p> |
