cs212 A Caesar cipher is an encryption scheme based on cycli

cs212

A Caesar cipher is an encryption scheme based on cyclic permutations of the alphabet, with the i-th letter of the alphabet replaced by the (i + n)-th letter of the alphabet. For example, in a Caesar cipher with a shift of 4, \"Caesar\" would be encrypted as \"Geiwev.\" Give three heuristics that might be used for solving Caesar ciphers. In a simple substitution cipher, each letter is replaced by another letter under some arbitrary one-to-one mapping. Which of the heuristics proposed for the Caesar cipher may be used to solve substitution ciphers? Explain. (Thanks to Don Morrison for this problem.)

Solution

the three heuristics that might be used for solving the caesar ciphers are:
1. try all possible keys. ie 25 alphabet. this is like trial and error method.
2. solving by doing some frequency analysis. As vowels will be there is most of the words in English, try to find the vowels in the word. According some analysis, alphabet E is the most frequent letter used in English. Replacing mostly used letters in encoded word with E would help in solving the encoded word.
3. To use N-gram approach. Mostly use the tri-gram approach which would help replacing the sentences like \"the\" in the encoded sentence. for words the tri-gram might not work.

The substitution cipher also uses N-gram approach similar to that of caeser cipher.

for further queries kindly get back