Notes on the ACA Decode routines:
(1) Our decoding routines should always be able to decode a cipher that has been encoded by our encoding routines.
(2) Decoding ciphers that were not encoded by our routines may or may not work. For example, there are alternate ways of encoding a Bazeries -- you can translate a number such as 1125 into English in more than one way. When there is more than one decoding alternative, we use the one that reproduces the examples in "The ACA and You" reference book.
(3) If you are trying to decode a cipher that you think was encrypted using a route that is not one of the choices in our routines, then you can insert the entire keysquare into the key box, and leave the route selector on "horizontal". For example suppose you made up a Playfair route with the key of CRIB along the square's main diagonal, and the remaining letters filled in along alternating diagonals. The key square would be:
To use this route in our playfair encoding or decoding routine, paste into the key box the entire keysquare taken off left to right: CHQWZDRKSXNEILTUOFBMYVPGA , and leave the route selector on "horizontal". (Click here for help in constructing such keysquares.)
(4) Similarly, our fractionated Morse and trifid routines expand the key word by appending the missing letters in alphabetical order. This misses cases where the key word is shifted. In those cases you must paste in the entire key yourself. For example, the key word in cipher AC-960, a fractionated Morse, is CZARISM POET. But entering this phrase alone into the key word box won't work because the key phrase is shifted to the right. Instead you must enter the entire key: DFGHJKLNQUVWXYCZARISMPOETB
(5) Sometimes the "key" that is given as a solution to a transposition cipher is not the key as defined in the "ACA and You" reference book. Instead you are sometimes given the inverse of the key. That is, you are given the "decoding key" instead of the "encoding key". These keys are inverses of each other. Given one, it's easy to calculate the other; this program will do the calculation for you.