The Cipher Challenge

There will be a series of transmissions of different ciphertexts representing different levels of cryptanalytic challenge.

Easy (1)

For the first challenge we shall provide:

• wheel patterns for all 12 wheels
• start positions for the M and S wheels.

The cryptanalyst just needs to find the K wheel starts and then decipher.

Hard (2)

For the second challenge we shall provide:

• wheel patterns for all 12 wheels;
• start positions for the M wheels.

The cryptanalyst needs to find start positions for the K and S wheels and then decipher.

Hardest (3)

For the third challenge we shall provide:

• wheel patterns for all 12 wheels
• no wheel start positions

The cryptanalyst needs to find start positions for the S, K and M wheels and then decipher.

Wheel Settings

All three cipher challenges will use the same wheel patterns. These are the same as the BREAM patterns that were used in WWII.

The Wheel patterns are:

bk1 ...xxxx....xx....x.xx..x..xx.x.xx.x.xxxx.

bk2 xx..xxx.xx...x.x.xx...x....xxx.

bk3 ..xxx.xx..x....xxx..xx.xx..xx

bk4 ..xx..x.xx..x..xx..x..xxxx

bk5 .x...x.xx..x...xxx.xxx.

bm1 xxx.x.xx..xx..xx...xxxx.x.xx.xx...xx....xxxx.xx..xx...xx....x

bm2 x.xxx.x.x.x.x..x.x.xxx.x.x.x.x.x.x.x.

bs1 ..x.x.x.x.x..x..x.xx.xx.x.x..xx.xxx..xxx...

bs2 ..x.xx.x.x.x.x.x.xx..xx.x..x.xxxx.....xxx..x.xx

bs3 x.x.x.x.x.x.x..x..xx.x.x.xxxx....xxx...xxx.xx..x..x

bs4 x.x..xx.x.x.x.x.x.xx.x....xx..xx..xx.xxxxx.x..x....x.

bs5 .x.x.x.x.xx...x.x..xxx.xxxx.xx.x....x...x..xx.xx..xx..x.x.x

The known wheel start positions for Challenge 1 will be:

M 22,12

S 10,28,18,23,26

The known wheel start positions for Challenge 2 will be:

M 22,12

There are no known start positions for Challenge 3

More information on using Virtual COLOSSUS to find the wheel start positions and Virtual TUNNY to decrypt the ciphertext can be found on http://www.codesandciphers.org.uk