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Encyclopedia > LOKI97
LOKI97
The LOKI97 round function
Designer(s): Lawrie Brown, assisted by Jennifer Seberry and Josef Pieprzyk
First published: 1998
Derived from: LOKI91
Key size(s): 128, 192 or 256 bits
Block size(s): 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. Image File history File links LOKI97_InfoBox_Diagram. ... Jennifer Seberry is Professor and Former Head, Department of Computer Science and the Director at the Centre for Computer Security Research at University of Wollongong, Australia. ... Josef Pieprzyk is a professor at Macquarie University in Sydney, Australia. ... In cryptography, LOKI89 and LOKI91 are block ciphers designed as possible replacements for the Data Encryption Standard (DES). ... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... In cryptography, a Feistel cipher is a block cipher with a particular structure, named after IBM cryptographer Horst Feistel; it is also commonly known as a Feistel network. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and γράφειν gráfein to write) is the study of message secrecy. ... Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ... On January 2, 1997 the National Institute of Standards and Technology, or NIST, called for cryptographers to propose a new standard block cipher for United States Government use in non_classified but sensitive applications. ... In cryptography, LOKI89 and LOKI91 are block ciphers designed as possible replacements for the Data Encryption Standard (DES). ... In cryptography, LOKI89 and LOKI91 are block ciphers designed as possible replacements for the Data Encryption Standard (DES). ... Jennifer Seberry is Professor and Former Head, Department of Computer Science and the Director at the Centre for Computer Security Research at University of Wollongong, Australia. ... Josef Pieprzyk is a professor at Macquarie University in Sydney, Australia. ...


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. The Data Encryption Standard (DES) is a cipher (a method for encrypting information) selected as an official Federal Information Processing Standard (FIPS) for the United States in 1976, and which has subsequently enjoyed widespread use internationally. ... Feistel cipher - Wikipedia /**/ @import /skins-1. ... In cryptography, the Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the U.S. government. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... The key-schedule of DES In cryptography, the algorithm for computing the subkeys for each round in a product cipher from the encryption (or decryption) key is called the key schedule. ...

Overall LOKI97 Cipher Structure
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. Overall structure of the LOKI97 block cipher. ... Overall structure of the LOKI97 block cipher. ... In cryptography, a substitution box (or S-box) is a basic component of symmetric key algorithms. ... In cryptography, a substitution box (or S-box) is a basic component of symmetric key algorithms. ... In cryptography, a substitution box (or S-box) is a basic component of symmetric key algorithms. ...


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. In cryptography, LOKI89 and LOKI91 are block ciphers designed as possible replacements for the Data Encryption Standard (DES). ... In cryptography, LOKI89 and LOKI91 are block ciphers designed as possible replacements for the Data Encryption Standard (DES). ... Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ...


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. On January 2, 1997 the National Institute of Standards and Technology, or NIST, called for cryptographers to propose a new standard block cipher for United States Government use in non_classified but sensitive applications. ... Differential cryptanalysis is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. ...


See also

This picture, from an 18th century Icelandic manuscript, shows Loki with his invention - the fishing net. ... On January 2, 1997 the National Institute of Standards and Technology, or NIST, called for cryptographers to propose a new standard block cipher for United States Government use in non_classified but sensitive applications. ...

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.

Lars R. Knudsen Lars Ramkilde Knudsen (born February 21, 1962) is a Danish researcher in cryptography, particularly interested in the design and analysis of block ciphers, hash functions and message authentication codes (MACs). ... Together with Joan Daemen, Vincent Rijmen designed the Rijndael block cipher, which was selected as the Advanced Encryption Standard in 2000. ...

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