## Can you solve these crypto puzzles from the 1950s?

In the 1950s, a US company published weekly newspaper advertisements that included crypto puzzles. Here are three of these.

For the first time in over ten years, the FBI has published a challenge cipher. Can you solve it?

## Konstantin Hamidullin solves 26-letter Playfair challenge and sets new world record

Konstantin Hamidullin from Latvia has solved my Playfair challenge from November 2019. With only 26 letters, this is the shortest Playfair cryptogram ever broken.

## Four challenge ciphers from a children’s book

A children’s book from the 1980s contains numerous encrypted and hidden messages. Can a reader solve four of these?

## 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.