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In 1901 an unknown person sent an encrypted postcard from Iserlohn, Germany, to nearby Arnsberg. Can a reader decipher it?

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At the HistoCrypt in Uppsala, Craig Bauer gave a talk about famous cryptograms. Among other things, he defended his solution of the second Zodiac Killer cryptogram, which was heavily criticized by the readers of this blog.

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Two encrypted newspaper advertisements from 1875 are still unsoved. Is the first one the key to the second?

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A dog tag introduced by a Reddit reader bears an inscription that looks like encrypted text. Can a reader solve this cryptogram?

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A Donald Duck comic story, which was recently republished in a German Disney magazine, contains an encrypted message. The solution, if it exists, appears to be unknown. Can a reader break this cryptogram?

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Here’s a great challenge for my readers: Robert Bunch (1820-1881), a British spy in the US Civil War, left behind a number of encrypted messages that have never been deciphered. Can you solve this mystery?

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Only little is publicly known about the encryption systems used by the German terrorist organisation, RAF. A recent TV documentary that shows a number of encrypted RAF messages along with a key provides at least some basic information.

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A postcard from 1903 is encrypted in a dancing men code, like it is described in a famous Sherlock Holmes story. Can a reader decipher it?

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A fifth encrypted bottle post has been found in the river Alster in Hamburg. Still, nobody seems to have a clue what these strange messages mean.

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Here’s a postcard written in English that contains two kinds of encryption. Can a reader decipher this two-part cryptogram?