Hot answers tagged classical-cipher
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This can be broken. The exact nature of the attack will depend what modulus you use for the Hill cipher: are you working modulo a prime number, or working modulo 26?
Working modulo a prime $p$
A simple attack, with no fancy mathematics needed. One simple attack is to start by requesting the encryption of the 26 messages AAAA, BBBB, CCCC, DDDD, ..., ZZZZ.
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If you don't know the system, you just check one after the other:
frequency analysis of bigrams detects Ceasar and Playfair. Try Caesar first then Playfair.
Auto correlation method for Vigenere (for each x: count the number of occurances, where letter at position i and i+x are equal. For the correct codeword length, it will spike)
If you have a Hill ...
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