TheCodeBreakers
They rest on the
concept of the cipher alphabet. This is the list of equivalents used to transform the plaintext into the secret
form. A sample cipher alphabet might be:
plaintext letters abcdefghijklm
cipher letters LBQACSRDTOFVM
plaintext letters nopqrstuvwxyz
cipher letters HWIJXGKYUNZEP
This graphically indicates that the letters of the plaintext are to be replaced by the cipher letters beneath
them, and vice versa. Thus, enemy would become CHCME, and swc would reduce to foe. A set of such
correspondences is still called a "cipher alphabet" if the plaintext letters are in mixed order, or even if they
are missing, because cipher letters always imply plaintext letters.
Sometimes such an alphabet will provide multiple substitutes for a letter. Thus plaintext e, for
example, instead of always being replaced by, say, 16, will be replaced by any one of the figures 16, 74, 35,
21. These alternates are called homophones