Hi all, I don't know if you can help me or not, but you seem to be a group up on your cipher knowledge and I could do with a little guidance.
I am currently solving a puzzle that needs to use a combination of block ciphers and stream ciphers. I am on my way to doing it, but could do with help as to whether certain things are possible and what sort of cipher they are classed as.
I started out with a stream of what seemed like random letters eg. 12 digits long, and a six letter key word. Following the approach used in ciphers such as Vignere, I took the key word (when repeated) from the random stream to get a new 12 letter chain. In my mind, from what I have read, this is a stream cipher. Somebody else said it is more of a block cipher. Which is correct? Either way it was the right thing to do.
Now with my new chain of letters I need to do another deciphering step. Is it possible to decipher just the chain without a keyword, as I don't think I need that now? As in a code whereby each letter is influenced by the result of the previous letter being decoded? Is this closer to a stream cipher? I think that is where I am getting lost. Stream ciphers are definitely the key here as opposed to a standard Caeser or regular transposition code.
All the information I have found thus far online is connected to computer coding and there are no simplified examples, so any guidance would be appreciated.
I appreciate this is not your usual work, but thank you for reading it anyway.