CSE 107 Lecture Notes - Lecture 4: National Institute Of Standards And Technology, Triple Des, Linear Cryptanalysis
5 Oct 2018
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Expect aeks to succeed in 255 des computations, which is roughly 45 years! According to lc, you would"ve needed to store 244 i/o pairs, which requires 281 tb! Observation: the e computations can be performed in parallel. Des is considered broken b/c its short key permits rapid key-search! Block cipher 2des: {0,1}112 x {0,1}64 {0,1}64. Suppose k1k2 is a target 2des key and adaversary has m,c s. t. You can separate the searches over k1 and k2! (independent of each other) But these are huge, how can you run in shorter time: hash tables (you might get some false positives though!, sort them! (nlogn) For i = 1 to 256 do l[i] des(ti,m1) code to build the tables. For j = 1 to 256 do r[j] des-1(tj,c1) S { (i,j) : l[i] = r[j] } Find intersecting pairs ( but do we know they"re unique?) Maybe find a unique one? (a lot of false positives) kr(aminm) = 1.
