Akelarre (cipher)

Akelarre

General
Designers	G. Álvarez, D. de la Guía, F. Montoya, A. Peinado
First published	1996
Derived from	IDEA, RC5
Cipher detail
Key sizes	128 bits
Block sizes	128 bits
Structure	Lai-Massey scheme
Rounds	4
Best public cryptanalysis
Susceptible to ciphertext-only attack

Akelarre is a block cipher proposed in 1996, combining the basic design of IDEA with ideas from RC5. It was shown to be susceptible to a ciphertext-only attack in 1997.

Akelarre is a 128-bit block cipher with a variable key-length which must be some multiple of 64 bits. The number of rounds is variable, but four are suggested. The round function of Akelarre is similar to IDEA in structure.

After the successful cryptanalysis of Akelarre, its designers responded with an updated variant called Ake98. This cipher differs from the original Akelarre in the new AR-box (Addition-Rotation box), the swapping of words at the end of a round, and the addition of subkeys at the beginning of each round. In 2004, Jorge Nakahara, Jr. and Daniel Santana de Freitas found large classes of weak keys for Ake98. These weak keys allow a cryptanalysis faster than exhaustive search using only 71 known plaintexts, for up to 11.5 rounds of Ake98.

References

• G. Álvarez Marañón, A. Fúster Sabater, D. Guía Martínez, F. Montoya Vitini, A. Peinado Domínguez (1996). "Akelarre: a New Block Cipher Algorithm" (PDF/PostScript). Proceedings of SAC'96, Third Annual Workshop on Selected Areas in Cryptography. Queen's University, Kingston, Ontario. pp. 1–14. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)CS1 maint: multiple names: authors list (link)
• Niels Ferguson and Bruce Schneier (August 1997). "Cryptanalysis of Akelarre" (PDF). Proceedings of SAC'97, Fourth Annual Workshop on Selected Areas in Cryptography. Carleton University. pp. 201–212. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
• Lars Knudsen and Vincent Rijmen (August 1997). "Two Rights Sometimes Make a Wrong" (PDF/PostScript). Proceedings of SAC'97, Fourth Annual Workshop on Selected Areas in Cryptography. Carleton University. pp. 213–223. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
• Lars Knudsen and Vincent Rijmen (April 2000). "Ciphertext-only Attack on Akelarre". Cryptologia. 24 (2): 135–147. doi:10.1080/01611190008984238.
• J. Nakahara Jr., and D.S. de Freitas (2004). "Cryptanalysis of Ake98" (gzipped PDF). INDOCRYPT 2004, 5th International Conference on Cryptology in India. Chennai: Springer-Verlag. pp. 162–174. Retrieved 2007-02-05. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)