Class-5-12-RC-10 - Random Cryptographic Systems Random...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Random Cryptographic Systems Random Cryptographic Systems ASSUMPTIONS ABOUT CRYPTOGRAPHIC TRANSACTIONS and we also have Example Plaintext space Octopus Cod Oyster Tuna Ciphertext space us Analysis of the “ciphertext only” Attack Theorem 1 H(K| C) = H(K) + H(M) - H(C) Proof The key is independent of the message Thus H(K,C) = H(K,M) H(K,C) = H(K) + H(M) Recall that Thus H(C) + H(K| C) = H(K) + H(M) Q.E.D. C = E (M) Analysis of the “known plaintext ” Attack Theorem 2 H(K| C,M ) = H(K) - H(C|M ) Proof C = E K(M) H(K,C,M) = H(C,M) + H(K| C,M ) H(K,M) = H(C,M) + H(K| C,M ) H(C,M) + H(K| C,M ) = H(K) + H(M) H(K,C, M) = H(K,M) H(K,M) = H(K) + H(M) H(C,M) = H(M) + H(C| M) gives H(M) + H(C| M) + H(K| C,M ) = H(K) + H(M) Q.E.D. ...
View Full Document

This note was uploaded on 09/22/2010 for the course MATH MATH187 taught by Professor Math187 during the Spring '10 term at UCSD.

Ask a homework question - tutors are online