A team of computer scientists has improved the record for factorizing prime number products from 795 to 829 bit.

Last December, Jarl Van Eycke and Louie Helm solved a bigram-substitution ciphertext consisting of 750 letters – a new world record was reached. Now I have created a 600-letter bigram challenge. Can it be solved, too, or have we reached the end of the line?

Today I’m going to introduce an alternate reality game (ARG) created by US puzzle designer Zachary Epstein. It was launched only a few days ago.

Today I’m presenting a 24 letter message that has been encrypted with a Playfair cipher. Such a short Playfair cryptogram has never been solved before.

The 1980s rock band Arcadia published a few encrypted messages on their record covers and in a sheet music book. The solutions are not known to me.

The autokey cipher is a variant of the Vigenère cipher that was once considered unbreakable. With today’s means it can be deciphered. Can a reader solve the challenge I’m introducing today?

Cryptocurrency platform Phemex has published a picture puzzle with a 2.1 bitcoin price for whoever provides the solution.

Jarl Van Eycke and Louie Helm recently solved a bigram substitution ciphertext consisting of 1000 letters – the shortest one ever broken. Now I have created a 750-letter challenge of the same kind.

Today I’m presenting a 26 letter message that has been encrypted with a Playfair cipher. To my knowledge, such a short Playfair cryptogram has never been solved before.

At the NSA Symposium on Cryptologic History, I gave a presentation about brute-force attacks. After a subsequent discussion with Whitfield Diffie, I realized that we need a new DES challenge. Here it is.