| 摘要 |
PCT No. PCT/NL94/00245 Sec. 371 Date Apr. 12, 1996 Sec. 102(e) Date Apr. 12, 1996 PCT Filed Oct. 7, 1994 PCT Pub. No. WO95/10906 PCT Pub. Date Apr. 20, 1995A system for encrypting and decrypting digital data wherein the data is divided in packets of N blocks X(1) . . . X(N) of 2m bits, comprises an encryption device and a decryption device. The encryption device reverses the sequence of the blocks X(1) . . . X(N) before a XOR operation and next an encryption operation by means of an encryption algorithm E is carried out on each block of a packet. Thereby the following encrypted blocks Y(1) . . . Y(N) are formed: Y(1)=E [X(N)+IV], Y(i)=E [X(N-i+1)+Y(i-1)] for i>1 and i</=N. The encrypted blocks Y(1) . . . Y(N) are transferred by a sender in reversed sequence Y(N) . . . Y(1) to a receiver. The decryption device at the receiver obtains the original blocks X(1) . . . X(N) by carrying out a decryption operation by means of a decryption algorithm D and next a XOR operation on each block Y(N) . . . Y(l) received. Thereby the original blocks are obtained as follows: X(i)=D [Y(N-i+1)]+Y(N-i) for i=1, 2, . . . , N-1; X(N)=D [Y(1)]+IV. |
