Cryptography Reference
In-Depth Information
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Plaintext
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A ciphertext
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FIGURE 1.4
Simplified Drawing of a Typical Jefferson Cylinder
cylinder fell into the wrong hands, the cipher would become useless; in that case, one solu-
tion would be to reorder the wheels on the cylinder, ensuring that no unauthorized persons
receive this vital information.
1.19
HOMOPHONIC SUBSTITUTION CIPHERS
Another approach taken to thwart frequency analysis was the use of homophones. This was
a system of enciphering wherein letters that occurred more frequently in the language were
given multiple choices of ciphertext symbols. The more frequent a plaintext letter was, the
more choices it would have.
For quick reference, the relative frequencies of letters in typical English text are shown
again, in Figure 1.5.
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0
A
BCDEFGH I J KLMNOPQRSTUVWXYZ
Letter
FIGURE 1.5
Relative Frequencies of English Letters (percent)
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