| Problem number | Problem | Due date |
|---|---|---|
| 1 | 100 consecutive letters of random text
and the individual letter frequencies | 1/7 |
| 2 | Complete the solution. | 1/7 |
| 3 | Make a table showing the multiplicative inverses (reciprocals) modulo 26 of the numbers 1, 2, 3, 4, ... , 25, 26. (Some do not exist.) Keep a copy for your reference. | 1/8 |
| 4 | Handout: "Modular Arithmetic and Affine Ciphers" | 1/8 |
| 5 | Find all the solutions of
(a) 20 x = 4 (mod 30) (b) 20 x = 10 (mod 30). | 1/8 |
| 6 | Little Orphan Annie crypt | 1/9 |
| 7 | "The Gold-Bug" cipher | 1/14 |
| 8: not counted | Decipher this crypt: ITKO GKRV
(Autokey with priming key "P") | --- |
| Extra credit #1 | Solve the polyalphabet crypt introduced in class. | 12:30 1/14 |
| 9 | Submit two questions regarding the video Decoding Nazi Secrets that might be suitable for the next MCS 150 exam. Also submit the answers. | 1/16 |
| 10 | Decipher one of Sinkov's crypts #57-61.
See p. 182 for the keys. | 1/17 |
| 11 | Using a Playfair square based on the keyword "PALMERSTON" ...
(a) encipher "call home at once" and (b) decipher ZGGLS TSLTG. Using instead keyword "GUSTAV", decipher HSTAT GBVUN EQCA. (corrected) | 1/20 |
| 12 | Let g = gcd(345, 543).
(a) Find g. (b) Find integers s and t such that 345s + 543t = g. Solve 345 x = 12 (mod 543). | 1/23 |
| Extra credit | Solve the NSA challenge posted outside my office. | 1/31 |
| Extra credit | Solve the following transposition crypt with known plaintext "the probable": IPLAI HLTCH EFAOH ORWKR ACTIT AMLNO NPTRO DCEMO RTTBE LEXAR SABDI AEMSN PWOAS LUNOE EHR. | 1/29 12:30 |
| 13 | Solve Lewand p. 160 #3, or
turn in a Maple worksheet for Lewand pp. 166-169. | 1/31 |
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