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DesignersA.A. Moldovyan and N.A. Moldovyan
First publishedJanuary 2002
Derived fromSpectr-H64
Cipher detail
Key sizes256 bits
Block sizes64 bits
StructureFeistel-like network
Best public cryptanalysis
Differential attack using 256 chosen plaintexts

In cryptography, CIKS-1 is a block cipher designed in 2002 by A.A. Moldovyan and N.A. Moldovyan. Like its predecessor, Spectr-H64, it relies heavily on permutations of bits, so is better suited to implementation in hardware than in software.

The algorithm has a block size of 64 bits. It uses an 8 round structure in which half of the block determines the transformation of the other half in each round, similar to a Feistel cipher or RC5. In each round the key also undergoes a transformation dependent on the data. CIKS-1 uses four types of operations: data-dependent permutations, fixed permutations, XORs, and addition mod 4.

The designers of CIKS-1 didn't specify any key schedule for the cipher, but it uses a total key size of 256 bits. Kidney, Heys, and Norvell showed that round keys of low Hamming weight are relatively weak, so keys should be chosen carefully. The same researchers have also proposed a differential cryptanalysis of CIKS-1 which uses 256 chosen plaintexts.


  • B. Kidney, H. Heys, T. Norvell (November 12, 2003). "A Weight Based Attack on the CIKS-1 Block Cipher" (PDF/PostScript). Retrieved January 3, 2007. {{cite journal}}: Cite journal requires |journal= (help)CS1 maint: multiple names: authors list (link)
  • B. Kidney; H. Heys; T. Norvell (2004). "A Differential Attack on the CIKS-1 Block Cipher" (PDF/PostScript). Retrieved January 3, 2007. {{cite journal}}: Cite journal requires |journal= (help)

Further reading[edit]

  • Changhoon Lee; Deukjo Hong; Sungjae Lee; Sangjin Lee; Hyungjin Yang; Jongin Lim (2002). "A Chosen Plaintext Linear Attack on Block Cipher CIKS-1". In Robert Deng; Sihan Qing; Feng Bao; Jianying Zhou (eds.). Information and Communications Security: 4th International Conference, ICICS 2002, Singapore, December 9–12, 2002 : Proceedings. Springer. pp. 456–468. ISBN 9783540001645.