MAT331

Exercise 3: Simple Cryptography

Exercise 3: Simple Cryptography

- 1.
- Decode the following phrase, which was encoded using a affine
encoding cipher on a 27-letter alphabet (the letters a-z and a blank).
xgb dkjvmbkffcmtkrv m lkaerask mdbmwkfmezremzkmxrcm kkmfvkrx mxgvkmaskrvsc
- 2.
- Sometime soon, you will be emailed a message encoded by an affine
matrix cipher, as well as the few letters of the message. Decrypt it.
- 3.
- Recall that a Vignère cipher can be interpreted as a Caesar-like
cipher on
*n*-vectors, where*n*is the length of the key phrase. Can any affine encipherment on digraphs (two-character codes) be interpreted as a an affine matrix encipherment on 2-vectors? That is, suppose I encode a message by affine enciphering on digraphs. Can I get the same crypttext from the same plaintext using an affine matrix enciphering (using a matrix) on 2-vectors? If your answer is yes, prove it. If no, give a counter-example that cannot be so interpreted.