NTA-NET (UGC-NET) Computer Science & Applications (87) Networks, Virtualization, & Cloud Computing-Network Security and Privacy Study Material (Page 6 of 24)

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Feistel Cipher

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  • Block cipher having k bits in key and n bits in a block. So 2k possible transformations not .
  • Feistel suggested to use substitution and permutation alternatively to produce ciphertext.
  • Substitution: Each plaintext element is replaced by a corresponding element. Replacement is unique.
  • Permutation: The order of plaintext element is changed.

Feistel Cipher Suggests Confusion and Diffusion. – to Suppress Statistical Cryptanalysis

Diffusion

  • One plaintext digit affects in deriving the value of several ciphertext digit.
  • Message

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Design of Block Cipher

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Number of Rounds

  • More number of rounds, difficult for cryptanalytic attack.
  • Even if function F is easy to break, a greater number of rounds make cipher strength high.

Function F Design

  • F adds confusion. F must be difficult to evaluate through linear equations.
  • F must produce avalanche effect. One-bit change produces change in several b…

… (58 more words) …

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