If one strips down the English alphabet to only lower case letters, (eliminate c

Question

If one strips down the English alphabet to only lower case letters, (eliminate capitalization, white space, and punctuation), then there are 26 symbols, aka letters. We know from combinatorics that there are 26 factorial possible distinct permutations of these 26 symbols, which, is approximately 3x1025 which is about 50 moles, which is approximately the number of water molecules in a glass of water. In other words, there are as many substitution ciphers that operate on the English language as there are molecules in a glass of water. The key space for substitution ciphers is HUGE, and this would lead a naive person to beleive they are secure. Please try to explain why substitution ciphers are not secure. (And, PLEASE be concise.)

Explanation / Answer

The major insecurity with substitution ciphers is that the frequencies of letters are not masked at all. If an enciphered message was intercepted, the interceptor could look at the frequencies of each letter and compare them to the frequencies of English.

If the interceptor deciphers the first phrase then they would have an easy time deciphering the rest of the message.

Thats why substitution ciphers are not that secure.

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