New answers tagged classical-cipher
How secure is this cipher? At first glance, not very. It would appear to be vulnerable to a ciphertext-only attack, for example, the attacker can recover the plaintext given a ciphertext of about 10k (actually, he probably can deal with less), even assuming that all the attacker initially knows is that the plaintext is "ASCII English", and he has no ...
There are diagnostic programs that will tell you the cipher type from a statistical analysis. For example: http://bionsgadgets.appspot.com/gadget_forms/refscore.html tells you immediately that this cipher is a Playfair.
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