British comedian Chris Sievey, also known as Frank Sidebottom, left behind a number of encrypted messages. British Codebreakers deciphered them and will publish the solutions in a few days. Can a reader break these cryptograms beforehand?

In the 19th century, a sailor working on the Great Lakes kept an encrypted diary. Can a reader decipher it?

In a Kansas library an unknown person has written an encrypted message into a book. Can a reader solve this “book cipher”, which is probably not a book cipher?

In 1909, an unmarried woman in Santa Monica received a postcard encrypted in an unusual cipher. Can a reader break this encryption?

My readers have shown that a Playfair cryptogram consisting of only 40 letters can be broken. Here’s a Playfair challenge with only 30 letters. Can you break it, too?

German poet and translator Stefan George (1868-1933) created his own secret language. It has never been deciphered – probably because only two lines written in it have survived.

A Reddit user has posted a strange cryptogram engraved on a metal plate. Can a reader make sense of it?

A blog reader has told me about strange email messages he receives occasionally. Does a reader know what they mean?

A blog reader has sent me a picture of a medal that bears unusual inscriptions on both sides. Can a reader make sense of these?

A Reddit user recently purchased a cryptologic document from the Second World War. Can a reader make sense of it?