CSSE/MA479: Cryptography

Homework 2, due on the date listed on the schedule page (85 points)

• Decrypt at least 3 of your classmates' discussion forum posts (ones that you don't know already) and submit printouts of the plaintext (5 pts)
• Do the following written problems from Trappe and Washington, section 2.13. (Show your work, as discussed in Homework 1) #10, #11, #12, #13, #14 (10 pts each)
• Do the following computer problems from Trappe and Washington, section 2.14: #8 (decrypting Vigenere: 15 pts), #10 (decrypting Hill cipher: 15 pts). The Vigenere ciphertext is stored at the book's website here : http://www2.math.umd.edu/~lcw/MatlabCode/ciphertexts.m , or here, for your convenience:

  ocwyikoooniwugpmxwktzdwgtssayjzwyemdlbnqaaavsuwdvbrflauplooubfgqhgcscmgzlatoedcsdeidpbhtmuovpiekifpimfnoamvlpqfxejsmxmpgkccaykwfzpyuavtelwhrhmwkbbvgtguvtefjlodfefkvpxsgrsorvgtajbsauhzrzalkwuowhgedefnswmrciwcpaaavogpdnfpktdbalsisurlnpsjyeatcuceesohhdarkhwotikbroqrdfmzghgucebvgwcdqxgpbgqwlpbdaylooqdmuhbdqgmyweuik	

  Note: The last line of the ciphertext given in the book (mvswrvnqlszdmgaoqsakmlupsqforvtwvdfcjzvgsoaoqsacjkbrsevbel) is gibberish, even for ciphertext. Don't use it to solve the assignment.

  For each, submit a printout of your program (or a transcript of your Matlab/Maple session if you used the Appendix) and your results (the decrypted plaintext).

  Note: you may write a program to do this from scratch (that's what I did for Vigenere), or use the book's code, following the process given in Appendices (e.g, C.2 example 4 in Matlab). You reap what you sow: it's harder work to code from scratch, but you get more out of it. On the practical part of Exam 1 (week 3), you'll need to decrypt messages using these various ciphers using this software - doing this homework carefully and documenting it well is the best way to prepare.