Poly-alphabetic Ciphers.
Viginere System.
|
Solitaire Cipher.Solitaire Cipher. Wikipedia entry on Solitaire Ciphers. |
How to break these ciphers.Need link here to PMCC XL work.
|
Digraph CiphersThere is a huge variety of digraph ciphers. Most use a 26x26 grid with A-Z running across the top and down the side. The plaintext is broken up into two letter pairs. The first letter of the pair is used to find the x coordinate on the grid (across). The second letter gives the y coordinate (down). The grid square indicated contains the letter pair which is substituted for the original plain text pair, or vice versa in some cases. There are 676 double letter pairs which means that digraph ciphers are effectively substitution ciphers with an alphabet of 676 pairs. To break one of these ciphers use Digraph Counter. which counts the letter pairs. Compare the stats from this analysis with those of a large sample of English plaintext; see digraph statistics. Try to spot any "cribs" (known words or phrases) and use these to break into the letter grid. Once you have a few letter pairs in place it might be possible to work out how the letter grid was constructed. Digraph Tools Javascript tools for breaking most basic digraph ciphers. There are at leats 16224 variations on this sytem possible so do some frequency analysis work first. |
Challenges.Poly-Alphabetic Challenges. Challenges using the 26 letter english alphabet based on the cipher systems described in this section. Some of these are very hard indeed. Make sure you have fully understood the workings of the simpler cipher systems before tackling these. |
last updated 14th July 2008