## A challenge based on a 1919 cipher tool

After the First World War, Italian engineer Luigi Nicoletti invented a transposition cipher tool. Can you break a ciphertext I created with this device?

## Two new crypto games: “Krypto im Advent” and “The Codebreakers”

Two online games for crypto enthusiasts have been launched – one in Germany, one in Poland.

## Can you solve this Playfair cryptogram from 1939?

In a well-known codebreaking book from the 1930s, a Playfair-encrypted message with a (probably fictive) background story is provided. Can a reader break this cipher?

## Three crypto challenges created by master codebreaker Jim Gillogly

20 years ago, Jim Gillogly, a great codebreaker and reader of this blog, created three crypto challenges – a Playfair, a Double Playfair, and a Double Column Transposition. Can you solve them?

## A nice problem from the Students’ Olympiad in Cryptography

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

## Playfair cipher: Is it unbreakable, if the message has only 50 letters?

The Playfair cipher is an encryption method from the 19th century. Some say that a Playfair-encrypted message of 50 or less letters is still secure today, if the method is used properly. Let’s put this claim to the test.

## Puzzle yourself through the Christmas season!

Crypto puzzle games in the advent time have a long tradition. Here are two nice ones of this year’s season.