Assignment 1: Due Wednesday, February 4
1. The following ciphertext message was encrypted using a double transposition
cipher (of the type discussed in class), where spaces in the original message
have been eliminated.
rntacunesulearrfepiaocudfoometooivkhrngrewieotvtideenclalosnd
alsthamteetitegtaallnndlttcceihoanlisefaoesrmsleosdsidhneitec
iwhtcmbieetinrsongiayardiprelspeteaaytlpnthharteomdmecofrhom
Given that the row permutation used
is 9 2 5 0 6 4 10 12 11 3 7 1 8 and the column permutation is
6 8 4 12 1 5 0 9 13 2 3 7 10 11, decrypt the ciphertext to recover
the original plaintext. Insert spaces and punctuation so that the
recovered message is a valid English sentence.
2. The following is a ciphertext message generated using a simple
substitution cipher. Determine the plaintext and the key. Note that
the plaintext does not include inter-word spaces. Insert spaces and
punctuation into your recovered solution so that it is a valid English sentence.
KPQCCJXALZYXISBZQMZBUCJXGXLLTZMYBVXHZQJXLZMHXHJVQYBXOOVCJYZBXQPA
ASBCVMWXZYJTZMSMCJXCSASICJXCVHXGNZIVMWXBXMCOVMXHVMJVQJZVBKPQCCJX
ALZYXISBZQMZBUVJZDXQZVHVCCOVYXCJZCZLSMXQJSPLHXMYSPBZWXCJXYBXOKPQ
CCJXALZYXISBZQMZBUVJZDXQZVHVCCJBVYXOJZCVCXLLNSPCJBXXCVTXQVQCBPX
3. The following ciphertext message was encrypted using a
one-time pad, where the conversion between bits and letters is
the same as that given in the slides, that is,
E=000 H=001 I=010 K=011 L=100 R=101 S=110 T=111
Ciphertext: HKTS
a) Find 3 possible keys, that is, find 3 different "keys" that yield
valid plaintext messages.
b) Assuming you only have access to the ciphertext, how do you know
which of your "keys" (if any) is correct?
