CSE 107 Lecture Notes - Lecture 3: Block Cipher, And1
3 Oct 2018
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Procedure initialize: grabs a key randomly from the set of keys, but not giving it to adversary a. A can query fn on any input m d of its choice to get back c = ek(m) Eventually a will halt w/ an output k" which is viewed as the input to finalize. The tkr advantage of a is the probability that game returns true. Def: we say that k" keys is consistent w/ (m1,c1),,(mq,cq) if e(k",mi) = ci for all 1 <= i <= q. Key 00 is consistent with (11, 01) - with input 11 and key 00, it will map to 01. The game returns true if (1) the key k" returned by a is consistent with (m1,c1)(mq,cq) and (2) m1,,mq are distinct. A is a q-query adversary if it makes q distinct queries to its fn oracle. For j = 1 to q do mj xj; cj fn(mj)
