Two months ago, US book author A.J. Jacobs showed me the encrypted journal of psychologist Abraham Maslow (1908-1970). My readers did a good job in analyzing this cryptogram. Now, A.J. asks for additional help.

In 1943, the British intecepted an encrypted radio message sent from an airplane. Can a reader decipher it?

British WW2 soldier and prisoner of war Donald Hill kept a steganographic diary. A 13-minute TV documentary available on YouTube tells this story.

In 1908, an ecrypted postcard signed with “Somebody” was sent to a sobriety organisation in Northern Ireland. Can a reader decipher it?

Blog reader Christoph Tenzer has sent me a nice crypto challenge, based on an enhanced Caesar cipher. Can a reader solve it?

A sword showcased in a Havana, Cuba museum bears an encrypted inscription. Can a reader decipher it?

The homophonic Polybius is a simple but hard to break manual cipher. Can a reader break a message I have encrypted in this scheme?

A cipher disk introduced on Reddit looks like a mass-produced item from the 20th century. Does a reader have any information about this crypto tool?

Here’s an telegram from 1952 that might have been encrypted in a code. Can a reader find out which codebook has been used and decipher the message?

The cover of a well-known cryptography book shows a 16-letter cryptogram. Its solution is unknown.