encode · decode · hide · reveal
CLASSIFIED · OFFICE OF CRYPTANALYSISCipher Lab is a free workbench for six classic ciphers: Caesar, Atbash, Vigenere, Bacon, ROT13 and Rail Fence. Type on one side, watch the transformation on the other, and step through the substitution to see why it produces what it produces rather than just that it does. It also generates puzzles, which is what it was originally built for.
It runs entirely in your browser. Nothing you type is sent anywhere, there is no account, and it works offline once loaded, which matters if you are using it in a classroom with bad wifi. It was written for a cryptography week at a summer honours programme and then kept because the students asked for it.
Built by Elijah Purcell at Purcell Ventures LLC, a software company in Tuscaloosa, Alabama. His other free tools are indexed at purcellventures.co/tools.