## Homework 5 (due 2/14) CSC 233

We talked about different types of transposition ciphers (regular, irregular with crib). The book has no material on transposition ciphers in general; check out Helen Gaines' book Cryptanalysis (published by Dover).

After the midterm next week, we will talk about about mechanization of cryptology up to the time of WWI.

1. (Reading Assignment) As background for next week's topic read the first two sections of chapter 3 (up to page 124), covering the ADGVX and Vernam ciphers.

2. (Anagramming) In Rosemary's Baby, Mia Farrow takes the text

ALL OF THEM WITCHES

and rearranges the letters (i.e. anagrams the phrase) using a scrabble set, getting messages

COMES WITH THE FALL,
ELF SHOT LAME WITCH, and
HOW IS HELL FACT ME (dropping the second T)

Take your full name and see whether you can anagram it to spell something interesting (as you see by the examples, the sentence doesn't really have to make full sense, and you might consider dropping a letter or two). If your name doesn't give you anything interesting, use the name of your favorite book or movie (longer text is easier to anagram, make sure you have a lot of vowels).

3. (Simple regular Transposition Cipher)

You suspect the following text to have been the result of a regular transposition cipher.

```NPOOC TNSOR SVOIT EERGA HLEEE STPRU OBEET SOSUP SI
```
`a) Determine all possible key lengths (given that it is a regular cipher) in the range 4 - 12.`
`b) Test all possible key lengths (using the vowel test). Show results.`
`c) Try key lengths in the order suggested by b) and decrypt the ciphertext.`

4. (Transposition Cipher with crib)

You suspect the following text to have been the result of a transposition cipher, and you also suspect that the word “universe” appeared in the plaintext.

```NETET TEARH EGEMV HYCIO OSOTA RXERH
PEAAC TTVUB UOONA USTRD SVHE
```

a) Determine the likely length of the key (making use of the crib).

b) Reconstruct the plaintext.

Marcus Schaefer
Last updated: February 1st, 2006.