Applications of one-way hashing

• Suppose that A and B share a secret S.

• When A wants to communicate M to B:

  • for integrity and authenticity
    • A can send hash(M,S) together with M,
    • B can check hash(M,S).
  • for secrecy
    • A generates and sends a random nonce N, and hash(N,S) XOR M, instead of M,
    • only A and B can recover M.

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