Harry Welsch was a notable German cryptographer and mathematician during the Second World War. Not much seems to be known about him. Norwegian Enigma expert Frode Weierud would like to change this. Can my readers help?

A cryptogram that was found on the wall of a tunnel at the University of Texas has been discussed on several websites for years. Can a reader of this blog finally find the solution?

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?

I have an appearance in a YouTube video that introduces the ten most notable unsolved cryptograms. More than a million people have already watched it.

Canadian artist Zen Rankin has published two encrypted messages he created in his youth days. Can a reader break them?

An alleged cryptanalyst has published a new hypothesis about the Somerton Man cryptogram on Wikipedia. Does it make sense?

A video by US musician Laurie Anderson contains a spoken sequence of numbers. Can a reader make sense of it?

At first sight, an encrypted postcard from 1909 looks like many others I have introduced on this blog. However, the encryption method used is unusual.

An encrypted telegram from Italy is unsolved. Can a reader find the codebook that was used? Without the codebook, deciphering the telegram is as good as impossible.

Two days ago, on Thanksgiving, the NSA sent encrypted greetings to “every NSA employee across the globe”. Can you break this encryption?