Section 2.3 Due Sept 13th

  This section was on Vigenere Ciphers, which I wrote a code for last week; to encrypt and decrypt, but not to crack.  I am wondering how to write a good code to crack a substitution cipher, and a vigenere cipher, but my programming skills are not all that great.  And it seems to me that a cryptological attack would never be able to be done by a computer itself, that a cryptanalyst's skill and judgement can never quite be replaced by a machine.
  I think that this is the first cipher that has a real key.  I mean, the mapping on a substitution cipher is a key, but you have to change the whole mapping for it to be really different.  With a Vigenere cipher you just say "the new key is 'Moscow'" and you are done.  As long as the person knows how to spell the new key word, then you can change the key that easily, instead of writting down a list and sending it, which could be intercepted and would have to be consulted for each character that is written.  And it would be harder to crack than simple substitution.  Any simple substitution cipher is only barely strong enough to keep honest people honest.  But a vigenere cipher would take a pretty quick person to figure out, and a little but of comparing and testing.  Still not impossible to break, and still pretty easy with a computer I imagine, but very clever in how much more complicated to break for how little extra effort it is to do.