11 - Secure Channel Introduction Cryptography and Protocols...

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Introduction Secure Channel Cryptography and Protocols Andrei Bulatov
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Cryptography and Protocols – Secure Channel 11-2 Message Authentication Schemes (Reminder) A Message Authentication Scheme (MAC) consists of 2 algorithms (Sign, Ver) There is a key shared between the signer and the verifier (Alice and Bob). Alice sending a message P computes called a signature or tag. Then she sends (P,s) to Bob. Bob accepts the pair (P,s) only if ) ( P s k Sign = 1 ) , ( = s P k Ver
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Cryptography and Protocols – Secure Channel 11-3 Practical MACs Hash functions: Let h be a hash function Weaknesses of hash functions: collision attacks, length extension attacks HMAC-h (h is a hash function) a, b are constants UMAC MAC using block ciphers (to be considered later) s P k s P k = = ) || ( 1 ) , ( h Ver ) || ( ) ( P k P k h Sign = )) || ( || ( ) ( P b k a k P k = h h Sign
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Cryptography and Protocols – Secure Channel 11-4 Secure Channel: Security Requirements Alice sends a sequence of messages
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This note was uploaded on 03/05/2012 for the course CMPT 404 taught by Professor Andreia.bulatov during the Spring '12 term at Simon Fraser.

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11 - Secure Channel Introduction Cryptography and Protocols...

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