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.
llivtoueetnmnwfeehiastshiettaeinadhbteceesepatnimethir
etieyeoenhcwortrapcehsssxoixxthtiaeninafpotayincfeunil
nomibuyrnbsoefmkeeevothetsntaprrtnhailaewlyilrataeytrr
Given that the row permutation used
is 4 0 6 3 8 1 2 7 5 and the column permutation is
11 10 9 13 4 2 17 6 1 16 15 7 0 8 3 12 14 5, 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.
USVSHCNKOCUSMEXHQSIRUEGGEFSEGBSHPCQSGBKUP
BKGCGNCOBGKLLSKHGEEGBSHQGBKGPBKGMEXPSHSEH
NCOBGBKVSFSSUPKQUEGEGBSHPCQSGBKUPBKGMEXBK
ZFSSUPEXIZBKVSKLLSKHSZGEGBSNGEFSEGBSHPCQS
3. The following two ciphertext messages were 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 1: LSKR
Ciphertext 2: ILHS
However, a mistake was made, and both messages were encrypted using
the same one-time pad. Recover the plaintext messages.
Hint: Both plaintext messages consists of a single English dictionary word.
