Unformatted text preview: abytes. You and (e), be carefulclever, spaceefﬁcient memory: aEither design a separate source some for
CSELabs (d) needmachine. Your to use toosubmission should include onealgorithm or do use a few
gigabytes. such
research forYou need to use more clever, spaceefﬁcient algorithm. Either design one yourself, or do some
this question) an algorithm.)
research for such an algorithm.) (e) [Extra credit: 10 points] Find a (free) collision in hk : two distinct messages m1 , m2 such that
hk (m1 ) = hk (m2 ). For veriﬁcation purposes, use your student ID as the initial hash value
and provide the following values: the colliding hash (h4 in the ﬁgure), and its preimages in
the tail and the cycle (h3 and h100 in ﬁgure (b), respectively). For k > 80 this is worth 10
points, 72 < k ≤ 80 is worth 8 points, 64 < k ≤ 72 is worth 6 points, 56 < k ≤ 64 is worth 4
points, and 32 < k ≤ 56 is worth 2 points. Your main submission should include the collision
values, a brief description of your algorithm, and how to compile/run your source code on a
CSELabs Linux machine. Your moodle submission should include a separate source ﬁle for
this question.
(Note: for (d) and (e), be careful not to use too much memory: a straightforward algorithm
could use several terabytes for large enough k . You need to use a more clever, spaceeﬃcient
algorithm. Either design one yourself, or do some research for such an algorithm.) 3...
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 Spring '14
 Cryptography, hash function, Cryptographic hash function, Block cipher, tail length

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