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Lec 3: Game-Based Security Definition for PAKE

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Recap

  • PAKE: start from low-entropy password, end up in high-entropy session key
    • Dict polynomial-size

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  • Must be secure against man-in-the-middle adversary that can modify protocol messages back and forth
  • Secure means: only feasible attack is online guessing
    • How to formally define this??

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PAKE security definition: attempt 1.0

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Example execution of a 3-message flow protocol

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Attempt 1.1

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Attempt 2.0

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Attempt 2.1

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Adversary can be passive in a send session…

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Attempt 2.2

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