| General | |
|---|---|
| Designers | Laurel Intelligent Systems |
| First published | December 1993 |
| Cipher detail | |
| Key sizes | 64 bits |
| Block sizes | 64 bits |
| Structure | Substitution–permutation network |
| Rounds | 8 |
| Best public cryptanalysis | |
| Differential and linear cryptanalysis[1] | |
In cryptography, SXAL (substitution xor algorithm, sometimes called SXAL8) is a block cipher designed in 1993 by Yokohama-based Laurel Intelligent Systems. It is normally used in a special mode of operation called MBAL (multi-block algorithm). SXAL/MBAL has been used for encryption in a number of Japanese PC cards and smart cards.
SXAL is an 8-round substitution–permutation network with block size and key size of 64 bits each. All operations are byte-oriented. The algorithm uses a single 8×8-bit S-box K, designed so that both K(X) and X XOR K(X) are injective functions. In each round, the bytes of the block are first permuted. Then each byte is XORed with a key byte and an earlier ciphertext byte, processed through the S-box, and XORed with the previous plaintext byte.
The key schedule is rather complex, processing the key with SXAL itself, beginning with a null key and using permuted intermediate results as later keys.
MBAL[edit]
MBAL is an encryption algorithm built using SXAL that can be applied to messages any number of bytes in length (at least 8). It uses two 64-bit extended keys for key whitening on the first 64 bits. The algorithm consists of 9 steps:
- Pre-whitening
- Fm: An expanded version of SXAL applied to the entire message
- SXAL the block consisting of the first 4 and last 4 bytes
- Reverse the byte order of the entire message
- Fm
- Reverse
- SXAL the ends
- Fm
- Post-whitening
MBAL has been shown to be susceptible to both differential cryptanalysis and linear cryptanalysis.[1]
References[edit]
- ^ a b Schneier, Bruce (1996). Applied Cryptography (2nd ed.). John Wiley & Sons. p. 344. ISBN 0-471-11709-9.
External links[edit]
- ISO/IEC9979-0012 register entry (PDF), registered 23 October 1995
- U.S. patent 6,038,321, a patent on a communications system using SXAL/MBAL for encryption. Includes a description of SXAL/MBAL.
- Kobayashi, Kunio; Kazumaro Aoki (April 1999). "On linear cryptanalysis of MBAL ciphers (abstract)". Electronics and Communications in Japan (Part III: Fundamental Electronic Science). 82 (10). Wiley Interscience: 1–8. doi:10.1002/(SICI)1520-6440(199910)82:10<1::AID-ECJC1>3.0.CO;2-6. ISSN 1520-6440. Archived from the original on 2013-01-05. Retrieved 4 November 2009.
