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Many color laser printers add tiny yellow dots to each page they print. These dots encode the printer serial number and additional information. A recently published research paper reveals new information about this secret code.

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The hijacking of a Boeing 727 aircraft in 1971 is considered one of the most spectacular crimes in the history of the USA. After the hijacker had left the plane with a parachute, he was never seen again. According to a recent newspaper article, a deciphered cryptogram might now solve this mysterious case.

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A text written by the legendary German author Arno Schmidt contains a series of numbers that might represent encrypted texts. So far, nobody has found the solution of these cryptograms.

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The Book of Woo is a nice crypto puzzle created by comic artist Oliver Knörzer. If you want to solve it you should hurry up, as Oliver will soon publish the cleartext.

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HistoCrypt 2018 in Sweden was a great event. Here are a video made by me and a number of photos provided by Paolo Bonavoglia.

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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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In the intro of the German TV film “Im Namens meines Sohnes” a message is hidden. It is easy to solve.

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Here’s a nice crypto challenge I found in a paper about the Fourth International Students’ Olympiad in Cryptography. Can you solve it?