I've created a type of alphabet cipher in which each character is defined based on how distant it is (in the alphabet) from the preceding character.
So, assuming that A=0, B=1, C=2, etc., and you have a text input of "GOOSE," you would construct the output like this:
G (6) is 2 letters in front of E (4), so output is C (2);
O (14) is 8 letters in front of G (6), so output is I (8);
O (14) is 0 letters in front of O (14), so output is A (0);
S (18) is 4 letters in front of O (14), so output is E (4);
E (4) is 12 letters in front of S (18), so output is M (12).
One of the benefits of this type of cipher is that, unlike a Caesar cipher, it can't be broken using normal letter-frequency analysis, since the cipher-letter that represents each actual letter is not constant throughout.
I know very little about ciphers, so I'm assuming that this type of thing has been done before.
I'm curious: Does this type of cipher have a name -- and how easy is it to decipher, compared with other techniques?