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How would you go about solving basic custom made ciphers - e.g. one generated from this website

This is solving it without knowing the method of the cipher beforehand.

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closed as too broad by D.W., figlesquidge, e-sushi, AFS, rath Mar 22 '14 at 0:07

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

Read up on what types of cryptographic attack there are: what scenario are you working within? What powers are you giving the attacker? KPA/CPA/CCA ? – figlesquidge Mar 20 '14 at 12:05
up vote 2 down vote accepted

It's not clear what they actually mean by half of their things, or if there is any benefit of using them together. That site doesn't want to create any meaningful security, it's just to play around with numbers and letters.

  • They state to use Vigenere, that's okay, usual classic cipher, which can be broken if the text is long enough.
  • "Caesar box code": I have no idea what that means, unless they mean basically the same as a Vigenere cipher with length 5. This is kind-of pointless with a fixed block size, because that's one part of what makes Vigenere decent for a classical cipher.
  • "Skip letter code": No idea again, what they actually do. If you leave out letters, that's just not reversible. Going backwards comes down to guessing.
  • Railfence is a fixed transposition of letters, which is again pretty pointless.
  • Reverse: Same as railfence.
  • Encoding with morse or similar: Fixed codes like morse are just replacing one set of symbols by another, just takes time if you do it by hand.

What do we do if we don't know what was used? Well, first security by obscurity is bad in reality, because the scenario is unrealistic against serious adversaries. But for toying around: It's not that difficult just to try the various combinations of "algorithms". A computer will probably solve any such system within seconds. Building things from classical (broken) ciphers are not maknig things complicated for today's advanced machines.

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