SXAL/MBAL

SXAL
General
Designers
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

In cryptography, SXAL (Substitution Xor ALgorithm, sometimes called SXAL8) is a block cipher designed in 1993 by Yokohama-based . 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[]

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
F_m: 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
F_m
Reverse
SXAL the ends
F_m
Post-whitening

MBAL has been shown to be susceptible to both differential cryptanalysis and linear cryptanalysis.^[1]

References[]

^ ^a ^b Schneier, Bruce (1996). Applied Cryptography (2nd ed.). John Wiley & Sons. p. 344. ISBN 0-471-11709-9.

External links[]

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). Wiley Interscience. 82 (10): 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.

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[cryptanalysis-1] Schneier, Bruce (1996). Applied Cryptography (2nd ed.). John Wiley & Sons. p. 344. ISBN 0-471-11709-9.

[1]