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Lecture 7: Message Authentication Codes (IV)

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Recap: Secure MAC scheme

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Security proof

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Putting it together

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Recap 1: Hybrid argument

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intermediate game

original game

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Recap 2: Use random function instead of PRF

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Recap 3: Proof by reduction

  • Actual game
  • Simulation by reduction

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Variable-Length MAC Schemes

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Attempt 1

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Attempt 2

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Secure variable-length MAC scheme 1:�Hash-then-MAC

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message

compressed message

tag

 

 

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Secure variable-length MAC scheme 2:�CBC-MAC

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