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8 Authentication Security Protocols

by on Jul 17, 2009

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  • SANDEEPSINGH539 Sandeep Singh Alice and Bob share a secret key K. Suppose that someone suggests the
    following methods to allow Alice to securely authenticate to Bob.
    (a) (5 points) Bob generates a random message r, enciphers it using
    K under a secure block cipher scheme and sends the encrypted message
    to Alice. Alice decrypts it, adds 1 to it and sends the result encrypted
    with K under the same block cipher to Bob. Bob decrypts the message and
    compares it with r. If the difference is 1, then he is sure he is communicating
    with Alice; or else, as no one else knows the secret K, he is talking to an
    impersonator. Is this protocol secure? Why or why not.
    3 weeks ago
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8 Authentication Security Protocols 8 Authentication Security Protocols Presentation Transcript