LOKI97

LOKI97
General
The LOKI97 round function
Designers	Lawrie Brown, assisted by Jennifer Seberry and Josef Pieprzyk
First published	1998
Derived from	LOKI91
Cipher detail
Key sizes	128, 192 or 256 bits
Block sizes	128 bits
Structure	Feistel network
Rounds	16
Best public cryptanalysis
Linear cryptanalysis against LOKI97, requiring 2⁵⁶ known plaintexts (Knudsen and Rijmen, 1999).

In cryptography, LOKI97 is a block cipher which was a candidate in the Advanced Encryption Standard competition. It is a member of the LOKI family of ciphers, earlier instances being LOKI89 and LOKI91. LOKI97 was designed by Lawrie Brown, assisted by Jennifer Seberry and Josef Pieprzyk.

Like DES, LOKI97 is a 16-round Feistel cipher, and like other AES candidates, has a 128-bit block size and a choice of a 128-, 192- or 256-bit key length. It uses 16 rounds of a balanced feistel network to process the input data blocks (see diagram right). The complex round function f incorporates two substitution-permutation layers in each round.The key schedule is also a Feistel structure — an unbalanced one unlike the main network — but using the same F-function.

Overall LOKI97 Cipher Structure

The LOKI97 round function (shown right) uses two columns each with multiple copies of two basic S-boxes. These S-boxes are designed to be highly non-linear and have a good XOR profile. The permutations before and between server to provide auto-keying and to diffuse the S-box outputs as quickly as possible.

The authors have stated that, "LOKI97 is a non-proprietary algorithm, available for royalty-free use worldwide as a possible replacement for the DES or other existing block ciphers." It was intended to be an evolution of the earlier LOKI89 and LOKI91 block ciphers.

It was the first published candidate in the Advanced Encryption Standard competition, and was quickly analysed and attacked. An analysis of some problems with the LOKI97 design, which led to its rejection when shortlisting candidates, is given in the paper (Rijmen & Knudsen 1999). It was found to be susceptible to an effective theoretical differential cryptanalysis attack considerably faster than an exhaustive search.

References

L. Brown, J. Pieprzyk: Introducing the new LOKI97 Block Cipher
L.R. Knudsen and V. Rijmen, "Weaknesses in LOKI97", Proceedings of the 2nd AES Candidate Conference, Rome, March 22–23, 1999, pp. 168–174.
Wenling Wu, Bao Li, Denguo Feng, Sihan Qing, "Cryptanalysis of some AES candidate algorithms", Information and Communication Security - ICICS'99, LNCS 1726, pp 13–21, V Varadharajan (ed), Springer-Verlag 1999.
Wenling Wu, Bao Li, Denguo Feng, Sihan Qing, "Linear cryptanalysis of LOKI97", Journal of Software, vol 11 no 2, pp 202–6, Feb 2000.

External links

Block ciphers (security summary)

Common algorithms	AES (Implementations) Blowfish DES (Internal Mechanics, Triple DES) Serpent Twofish

Less common algorithms	Camellia CAST-128 IDEA RC2 RC5 SEED Skipjack TEA XTEA

Other algorithms	3-Way Akelarre Anubis ARIA BaseKing BassOmatic BATON BEAR and LION CAST-256 Chiasmus CIKS-1 CIPHERUNICORN-A CIPHERUNICORN-E CLEFIA CMEA Cobra COCONUT98 Crab Cryptomeria/C2 CRYPTON CS-Cipher DEAL DES-X DFC E2 FEAL FEA-M FROG G-DES GOST Grand Cru Hasty Pudding cipher Hierocrypt ICE IDEA NXT Intel Cascade Cipher Iraqi KASUMI KeeLoq KHAZAD Khufu and Khafre KN-Cipher Ladder-DES Libelle LOKI (97, 89/91) Lucifer M6 M8 MacGuffin Madryga MAGENTA MARS Mercy MESH MISTY1 MMB MULTI2 MultiSwap New Data Seal NewDES Nimbus NOEKEON NUSH PRESENT Q RC6 REDOC Red Pike S-1 SAFER SAVILLE SC2000 SHACAL SHARK Simon SMS4 Speck Spectr-H64 Square SXAL/MBAL Threefish Treyfer UES Xenon xmx XXTEA Zodiac

Design	Feistel network Key schedule Lai-Massey scheme Product cipher S-box P-box SPN Avalanche effect Block size Key size Key whitening (Whitening transformation)

Attack (cryptanalysis)	Brute-force (EFF DES cracker) MITM (Biclique attack, 3-Subset MITM attack) Linear (Piling-up lemma) Differential (Impossible Truncated Higher-order) Differential-linear Integral/Square Boomerang Mod n Related-key Slide Rotational Timing XSL Interpolation Partitioning Davies' Rebound Weak key Tau Chi-square Time/memory/data tradeoff

Standardization	AES process CRYPTREC NESSIE

Utilization	Initialization vector Mode of operation Padding

Cryptography

History of cryptography Cryptanalysis Cryptography portal Outline of cryptography

Symmetric-key algorithm Block cipher Stream cipher Public-key cryptography Cryptographic hash function Message authentication code Random numbers Steganography

LOKI97

See also

References

External links