The Vatican owns some encrypted manuscripts waiting for decryption. Can you find the solution for an archive manuscript from 1539-1548?

The Vatican owns some encrypted manuscripts waiting for decryption. Can you find the solution for an archive manuscript from 1535/1536?

The Vatican owns some encrypted manuscripts waiting for decryption. Can you find the solution for a message from 1721?

On November 3rd, 1509, Catherine of Aragon wrote an encrypted letter to her father. What did she tell him?

The Secret Archives of the Vatican keep a large collection of ciphertexts from papal correspondence. The keys of these manuscripts have been destroyed, or are kept elsewhere and been forgotten. Can you find out how to decipher the letter from March 14, 1625?

The Main Library of the Vatican owns some encrypted manuscripts, waiting for decryption. Can you find the solution to the letter from 1628?

Many telegrams that date from the Spanish Civil War (1936 - 1939) still remain undisclosed. It is assumed that these telegrams were encrypted using the Spanish Strip Cipher. Try to find the plaintext of this original telegram.

In 1586 the famous French mathematician Blaise de Vigenère published a picture of the night sky and claimed that a message was concealed in it. Can you find out how to decipher this message?

In 2006 the distributed "M4 Message Breaking Project" under the lead of Stefan Krah aimed at decrypting three ENIGMA M4 messages from the time of World War II. Two of the three messages where decrypted within the first weeks. However, the third message withstood despite all efforts and remained unbroken. Today, the M4 project has been discontinued with the last message still unbroken. The task of this challenge is to break this very last message - after all, a few years have past since the project was discontinued and cryptanalysis and computational power also advanced during this time. Note: The solution was published here: http://www.enigma.hoerenberg.com/. You can't get points for solving it any more, but you can still use it as a good training experience.

An unsolved FBI case: In 1999, an encrypted message was found in the pockets of a murder victim. No one was able to decrypt it so far.

In 1939, the Russian-born Briton Alexander D'Agapeyeff published a book named "Codes and Ciphers". This book contains a ciphertext that was meant as an exercise. So far, nobody has been able to decrypt this ciphertext. In later editions of his book, this exercise was omitted – possibly because he had forgotten the solution himself. D'Agapeyeff may have made a mistake during the encryption procedure, which makes it now difficult to find the cleartext.

In 1897, the English composer Edward Elgar sent an encrypted message to a lover. So far, nobody has been able to decrypt it. This message is known today as the "Dorabella Cipher".

The double columnar transposition is considered one of the best manual encryption systems. Many secret organizations have made use of it or still use it today. As there are only a few publications on this method, it is not clear if and how a well-constructed double transposition cipher can be broken.

Kryptos is a sculpture made by the US artist Jim Sanborn. It is located next to the headquarters of the CIA in Langley, VA. An encrypted message was written on the sculpture. The message consists of four independent parts. The first three parts have been solved, but the fourth one has so far withstood every attempt at decryption.

During World War II, the Italian solider Antonio Marzi worked as a radio operator. He created more than 230 pages full of enciphered notes about his experiences. Unfortunately, he forgot one step of his enciphering method. Still today, his records have never been decrypted.

In 1885, the US businessman James Ward published a booklet about an allegedly true story of a hidden treasure. According to the story, in 1823, a man named Thomas Beale hid several tons of gold and silver in a secret place and described the location of it in three encrypted messages. One of these messages was cracked, but it doesn't contain enough information to locate the treasure. The two other messages are unsolved.

The author of the German book "The Art of Deciphering", written 1808 remains unknown. However, the editor signs the preface with a cipher (Semicolon Plus One Triangle Plus Circle Period). Is this the encrypted name of the author?

In 1923, a member of the Ku Klux Klan sent an encrypted telegram to one of his colleagues. This telegram could be preserved. More than 60 years later, the US mathematician Cipher Deavours examined the telegram and was able to decipher it. In 1989, he published some of the details about the solution in the magazine Cryptologia („A Ku Klux Klan Cipher“, edition 3/1989). However, he didn‘t tell the complete solution – the last part was left to the reader as an exercise.