Crypto puzzle games in the advent time have a long tradition. Here are two nice ones of this year’s season.


The Reddit discussion group /r/codes is a forum for cryptographic questions of all kinds. Occasionally, interesting unsolved cryptograms can be found there.


The fifth episode of HISTORY’s Zodiac Killer documentary revealed an alleged solution of the infamous Z340 cryptogram. Does it make sense?


Four episodes of the Zodiac Killer documentary on HISTORY have aired now. The fourth one ended with Craig Bauer saying that he has broken Z340. Will episode 5 tell us the solution?


In 2013 the German intelligence service BND published four challenge ciphers. To my knowlege, the solutions have never been published.


In 1935 US president Franklin D. Roosevelt received an encrypted letter from an anonymous person. The solution of the main part is not known.


Alexander Hamilton, one of the Founding Fathers of the United States, has become especially popular since a musical was written about him. Hamilton left behind a 26×26 turning grille.


In the novel Mathias Sandorf by Jules Verne the use of a Turning Grille is described. Does a reader know other encrypted messages of this kind?


In 1873 George Furlong, official at the soccer club Luton Town FC, sent an encrypted letter to his sister. Can a reader break this encryption?


A postcard from 1906 is written in a combination of Morse code, numbers, and letters. Can a reader solve this unusal cryptogram?