Home > CS177 > Homework 4

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Ignore the numbers 1,2,3, etc. at the corners of your papers. Your scores are shown out of 12 points (three per problem (3x4=12 (but only in base 10 (that's ten (not two in binary (LISP, anyone?)))))).

Notes

Just general notes, cause there's nothing more to be said really (look at the solutions).

First of all, write down everything! Instead of simply saying that this appears to be a monoalphabetic substitution, say why. For example, the letter frequencies might look like a permutation of English frequencies, ruling out a transposition-only cipher and a polyalphabetic cipher. If the frequencies are not a cyclic shift of English letter frequencies, then it is probably not just Caesar.

Some people wrote down what they tried, but more important is what conclusions could be drawn from those tests. Describing your efforts won't guarantee you partial credit when you can't crack a cipher, but it certainly won't hurt.

Lastly, if you are asked to cryptanalyze a cipher again in this class, please include at least the beginning of the plaintext. Some people only put the keys but honestly, it's just a cut and paste.

Stats

In case you're curious, 63 out of 65 students got number one, 51 got number two, 49 got number three, and no one got the last.

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