| 释义 |
cipher A primitive means of encrypting a message—the 26 letters of the alphabet are permuted and every occurrence of a particular letter in a text is substituted for its replacement to make the ciphertext. A very basic example is Caesar ciphers, where each letter is shifted by some fixed amount to find its replacement, for example ABCD…being replaced by RSTU…. Even though there are 26! > 4×1026 ciphers, frequency analysis can quickly reduce the possibilities, and so ciphers are easy to decrypt.
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