From ancient languages to modern cryptographic challenges released by government agencies like the CIA these are 25 famously unsolved ciphers and codes that you won’t be able to break.
20. D’Agapeyeff Cipher
Alexander d’Agapeyeff wrote an elementary book on cryptography in 1939 entitled Codes and Ciphers. In the first edition he included a challenge cipher. It was never solved and even Alexander embarrassedly admitted later that he no longer knew how he’d encrypted it.
15. Richard Feynman’s Challenge Ciphers
In 1987 a message was posted to an internet cryptology list saying that Caltech Physics Professor Richard Feynman was given three samples of code by a fellow scientist at Los Alamos. Only one was ever solved.
A script which first appeared in about 2900 BC in Susa, in south-western Persia (modern Iran). It has yet to be deciphered and the language it represents is unknown.
5. Shugborough Inscription
O-U-O-S-V-A-V-V. These letters are carved into a stone monument on the grounds of Shugborough Hall in Staffordshire, England. In spite of much speculation no one has ever managed to figure out their meaning.