I've been interested in whether a Vigenere cipher without key repetition can be solved. If the key is random, it is a one-time pad and is theoretically unbreakable. On the other hand, if the key is a natural language text, I heard such a cipher (called a running key cipher) can be solved. But how?
I uploaded a new article about this: "Solving Running Key Ciphers (Manually/Digitally)".
It's a fun topic. I implemented both the Griffing and the Reddy and Knight algorithms in C, but it is not entirely clear what the Reddy and Knight algorithm was doing. For example what exactly does "sample" mean in the description? I didn't get the kind of results claimed. For Griffing, we have 7-gram data from AZDecrypt now, so that works a bit better.
ReplyDeleteI saw I'm not the only person who didn't understand what Reddy and Knight were doing. I did write to Reddy but didn't hear back.
https://crypto.stackexchange.com/questions/75559/running-key-gibbs-sampling