A French magazine article reports on an encrypted diary written by a pedophile priest. The plaintext is not known to me. Can a reader break it?

A recent book mentions a cipher used by a German spy during the Second World War. Can you break a message I encrypted with this method?

A few years ago, German late-night show host Stefan Raab presented a number puzzle in his show “TV total”. It involves cryptography and should be easy to solve for readers of this blog.

Various codebreakers have solved thousands of original Enigma messages from World War II over the last few years. Here’s a message of this kind that is still unsolved. Can my readers help?

In 1921 an encrypted telegram was sent from the Portuguese embassy in Berlin to Lisbon. The plaintext is known, but the encryption method used isn’t. Can a reader help?

HistoCrypt 2019 will take place from June 23-26, 2019 in Mons, Belgium. Here’s the Call for Papers. Apart from scientific papers, non-academic presentations are invited.

Just like every end of year, I am awarding the Golden Alice for outstanding achievements in the field of crypto history and codebreaking. Here are the winners 2018.

In 2016 several Brazilian newspapers reported on two encrypted letters sent by imprisoned members of the criminal organization PCC. Can my readers help to decipher the letter excerpts that are publicly available?

In 1911, the British consul in Lüderitz, German South West Africa, sent an encrypted telegram to the foreign ministry in London. Can a reader break this encryption?

Im ersten Teil des Apollo-8-Artikels berichtete ich vom Wettlauf der Amerikaner und Sowjets im Weltraum. Der erste Teil endete mit der erfolgreichen Apollo-7-Mission. Nun stand die nächste Mission an – aber die konnte nicht wie geplant durchgeführt werden.   Seid Ihr verrückt?! Laut Planung wäre als nächstes der bemannte Test des Lunar Modules, also der…