A Reddit user recently purchased a cryptologic document from the Second World War. Can a reader make sense of it?

“The Professional”, a French movie with Jean-Paul Belmondo, involves an encrypted telegram. The plaintext and the ciphertext are known. Is the encryption real?

A telegram sent by a British colonel in 1916 still waits to be solved. The encryption method used might be a letter-pair substitution.

Blog reader Christoph Tenzer has solved the Rubik’s Cube challenge I introduced last October. His work is an amazing act of cryptanalysis.

The encrypted inscription on the Kryptos sculpture is one of the most famous crypto mysteries in the world. Recently, a TV documentary about Kryptos was made. Here’s my making-of report.

In 1910, a man living in Bedford, Ohio, received an encrypted postcard. Can a reader decipher it?

In 1909, a woman living in Toledo, Ohio, received an encrypted postcard. Can a reader decipher it?

A few years ago, online magazine “Naked Security” ran a steganography competition. The participants had to hide a given message in an inconspicuous letter using a method developed by British cipher experts in WW2. The results were quite impressing. Can a reader do better anyway?

A Reddit user has posted scans of something that looks like a small codebook. It was found in a prison. Can a reader say more about it?

Alex from the Ukraine has provided me pictures that show two sculptures with an encrypted or abbreviated inscription. I have never seen anything like this before, let alone do I know what the inscriptions mean. Can a reader help?