Linear statistical weakness of alleged RC4 keystream generator

  • Authors:
  • Jovan Dj. Golic

  • Affiliations:
  • School of Electrical Engineering, University of Belgrade, Beograd, Yugoslavia

  • Venue:
  • EUROCRYPT'97 Proceedings of the 16th annual international conference on Theory and application of cryptographic techniques
  • Year:
  • 1997

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Abstract

A keystream generator known as RC4 is analyzed by the linear model approach. It is shown that the second binary derivative of the least significant bit output sequence is correlated to 1 with the correlation coefficient close to 15ċ2-3n where n is the variable word size of RC4. The output sequence length required for the linear statistical weakness detection may be realistic in high speed applications if n ≤ 8. The result can be used to distinguish RC4 from other keystream generators and to determine the unknown parameter n, as well as for the plaintext uncertainty reduction if n is small.