Ciphers Versus Codes
In non-technical usage, a "(secret) code" typically means a "cipher". Within technical discussions, however, the words "code" and "cipher" refer to two different concepts. Codes work at the level of meaning—that is, words or phrases are converted into something else and this chunking generally shortens the message.
An example of this is the Telegraph Code which was used to shorten long telegraph messages which resulted from entering into commercial contracts using exchanges of Telegrams.
Ciphers, on the other hand, work at a lower level: the level of individual letters, small groups of letters, or, in modern schemes, individual bits and blocks of bits. Some systems used both codes and ciphers in one system, using superencipherment to increase the security. In some cases the terms codes and ciphers are also used synonymously to substitution and transposition.
Historically, cryptography was split into a dichotomy of codes and ciphers; and coding had its own terminology, analogous to that for ciphers: "encoding, codetext, decoding" and so on.
However, codes have a variety of drawbacks, including susceptibility to cryptanalysis and the difficulty of managing a cumbersome codebook. Because of this, codes have fallen into disuse in modern cryptography, and ciphers are the dominant technique.
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Famous quotes containing the word codes:
“We must trust infinitely to the beneficent necessity which shines through all laws. Human nature expresses itself in them as characteristically as in statues, or songs, or railroads, and an abstract of the codes of nations would be an abstract of the common conscience.”
—Ralph Waldo Emerson (18031882)