www.xarg.org/tools/caesar-cipher/ This site has software for encoding and decoding messages with many different ciphers.

mentalfloss.com/article/27921/how-cryptic-4-famous-unsolved-ciphers-and-codes This article describes four famous unsolved ciphers and codes.

www.youtube.com Search for the BBC TV film The Strange Life and Death of Dr. Turing, a 50-minute documentary film about the British code breaker and war hero.

www.youtube.com Search for the BBC TV film Bletchley Park’s Lost Heroes, a one-hour documentary film revealing the secret story of how two men hacked into Hitler’s personal super-code machine.