Fundamentals of information theoretic cryptography

• Shannon - 1949

• Unicity Distance - quantity of ciphertext required to uniquely determine plaintext

  • H(K)/(|M|-H(M))
  • H(K) = information content of the key
  • H(M) = information content/symbol of message
  • |M| = length of message
  • When H(K)/(|M|-H(M))=1, the cipher can be broken - given enough time

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