3.4.1.cipher.txt

3.4 Problems
(1) One issuewith substitution ciphers is the difficulty of remembering the key. There
is a version of the substitution cipher that uses a key word that makes it easier
20 3 Substitution Ciphers
to remember. To set this up, pick a key word that has no repeated letters (or else
delete the repeated letters). Then, append to the key word all the unused letters in
the alphabet, starting from the last letter in the key word. This is a permutation of
the letters in the alphabet, and it serves as the key. For example, if the key word is
LIME, then the full key would be LIMEFGHJKNOPQRSTUVWXYZABCD. That
means that we encrypt a as L, b as I, and so forth.
The message
VOQDK MABJJ DZAXC ABAEE YCEVC OGDZH RGAJR
UQDKZ KHJOV GHJRG CAJCJ UCKBV LCGHC
was encrypted in this way using the key word APRICOT. What is the plaintext
message?