December 2021
Beginner
550 pages
20h 33m
English
Ciphers come in two basic forms:
Transposition ciphers—A transposition cipher rearranges characters or bits of data.
Substitution ciphers—A substitution cipher replaces bits, characters, or blocks of information with other bits, characters, or blocks.
A simple transposition cipher writes characters into rows in a matrix and then reads the columns as output. For example, write the message “ATTACK AT DAWN” into a four-column matrix, as shown in FIGURE 7-2.
FIGURE 7-2 A transposition cipher.
Then, read the information in columns: ACDTKATAWATN, which would be the ciphertext. The key would be {1,2,3,4}, ...
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