In 1924, British mountaineers George Mallory and Andrew Irvine died trying to be the first to climb Mount Everest. An encrypted telegram reported the drama to their homeland. A blog reader identified the codebook that was used, but there is still one word, the meaning of which is unknown.

In 1926 a US newspaper published a series of crime stories that involved encrypted messages. Here are four of them. Can you break them?

Craig Bauer, mathematics professor and crypto history expert, lets his students solve old ciphertexts as homework. Here are three especially interesting cryptograms Craig’s students have to break.

Already 30 years ago, US historian Albert C. Leighton collected historical cryptograms and tried to coordinate the study of these. He even thought of an equivalent of today’s crypto history conference, HistoCrypt. To my regret, nobody seems to know what happend to his collection after his death.  

Two years ago, I blogged about an encrypted notebook from the Soviet Union. Within a few days, a reader solved this crypto mystery. It is high time that I introduce this solution in a blog post.

The Rohonc Codex, one of the world’s most famous crypto mysteries, appears to have been solved. Here are the details about the solution.

The Rohonc Codex, one of the world’s most famous crypto mysteries, appears to have been solved. And yes, I believe this solution is correct.

English actress Diana Dors left behind an encrypted message. This cryptogram allegedly leads to two million pounds.

In 1934, an inmate of the Ohio State Penitentiary tried to hand an encrypted message to a visiting woman. A warden intercepted the message, a codebreaker in Washington could decipher it. Can a reader figure out what kind of cipher was used?

In 1948, an anonymous codebreaker deciphered an encrypted message by British parapsychologist Robert Thouless. The solution is known. Can a reader find out how the successful attack worked?