CSE 107 Study Guide - Fall 2018, Comprehensive Midterm Notes - Block Cipher, Ciphertext, Triple Des
12 Oct 2018
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Data privacy: ensure adversary does not see or obtain the data message (m) Data integrity: ensure m really originates w/ alice and has not been modified in transit. One cannot anticipate an adversary strategy in advance; infinite possibilities! Each letter maps exactly to the same letter. Therefore you can just play around with the letters and use common sense to figure out the table. Theorem: otp is perfectly secure as long as only one message encrypted. Limitation: if |m| > |k|, then no scheme is perfectly secure. Security of a practical system must rely not on the impossibility, but the computation difficulty of breaking the system. We might say no attack using <= 2160 time succeeds w/ probability >= 2-20 . There is no known alg to factor a huge number in a practical amount of time. {0,1}n is the set of n-bit strings and {0,1}* is the set of all strings of finite length.
