Bruno Borges, a Brazilian student who has been working on an “alien project”, has mysteriously vanished from his home. In his room he left behind numerous encrypted notes. Can a reader break his code?

On Friday the Heinz Nixdorf Museum will broadcast a number of radio messages encrypted with an Enigma. Codebreaking experts in Bletchley Park will try to decipher these cryptograms with WW2 technology. Enigma experts will try the same with computer support.

An inscription found on the inside of an old fiddle has never been deciphered.

The Riverbanks Ripper was a serial murderer, who killed nine people in the 1970s. He was never identified. At one of the crime scenes he left behind an encrypted note that is unsolved to date.