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

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?

In 1888, an encrypted advertisement was published in the “Daily Chronicle”. Can a reader decipher it?

Christopher Columbus frequently used a signature that included seven letters not belonging to his name. Do they represent an abbreviation?

At the hacker conference 44CON 2019, wich took place in September in London, I gave a talk about Cold War cryptography. Here’s a professionally produced video of it.

Sometimes, deciphering a cryptogram is easier than reading the deciphered message. Here are two plaintexts I have difficulties to understand.

In the end credits of the 2010 movie “Fair Game” some letters are marked. Do they spell out an encrypted message? Nine years after the release of the film, this question is still unanswered.

I’m looking forward to HistoCrypt 2019 (June 23-26 in Mons, Belgium). Among the speakers are many readers of this blog.

My readers have shown that a Playfair cryptogram consisting of only 50 letters can be broken. Here’s a Playfair challenge with only 40 letters. Can you break it, too?

The four cryptograms contained in a book partially written by famous German author Arno Schmidt are among the most interesting I have seen recently. My readers have provided some additional information about them.