Discovered in 1903, the Phaistos Disk is the most important example of hieroglyphic inscription from ancient Crete. It was found together with the Linear A tablet and other objects dating back to 1700-1600 BC (Neo-Palatial period). The spiral-arranged hieroglyphs impressed on a clay disk make up groups that are separated from each other by vertical lines and it is thought that each of this group should represent a word. 45 signs have been distinguished of which only few can be identified if related to the hieroglyphs used in the Proto-Palatial period. Some researchers suggest that the disk presents a religious ritual, while others claim it would render a list of soldiers, or a more current version states that it is a document written in the Hittic language, in which a kings discusses the foundation of the Palace of Phaistos.

The Voynich Manuscript became one of the most famous subjects of historical cryptography that not a single codebreaker or cryptographer has managed to crack and not even a single word from the 232-page Manuscript was decoded. At least 400 years old, this encrypted manuscript contains drawings of unidentified plants, some kind of herbal recipes, astrological diagrams and several small human figures in strange contraptions.

Discovered and named by Arthur Evans, Linear A is one of two scripts used in ancient Crete, that hasn’t been completely deciphered yet. Although Linear B has been deciphered by Michael Ventris in 1952 and the two scripts share many of the same symbols, using the syllables of Linear B in deciphering Linear A creates words that do not belong to any known language. While Linear B was used to write Mycenaean Greek, Linear A has been dubbed Minoan or Eteocretan, being related to a period in Cretan history that preceded the series of Mycenaean Greek invasions. Some researchers believe that Linear A has a connection with The Phaistos Disk.

Beale’s cyphers actually contain directions to a buried treasure. The story goes that around 1820, a man named Beale, buried two wagons full of treasures at a secret location in Bedford County, Virginia and then disappeared without a trace, but not before leaving a small locked box with a local innkeeper. Seeing that, after years, the man did not return for his box, the innkeeper opened it and discovered encrypted messages. Although one of the innkeeper’s friends spent 20 years to decipher them, he only managed to crack one, describing in detail al content of the treasure and a general location. Nevertheless, the other messages which should have presented the exact location of the treasure could not be deciphered, although many people came up with different (unsuccessful) solutions.

The Dorabella Cipher is the cryptic work of Edward Elgar, famous for his “Enigma Variations” - which is in itself a musical cryptogram – addressed on the 14th of July 1897 to a young friend, Miss Dora Penny, in a letter. The cipher still presents a challenge nowadays.

The inventor of the Chaocipher is John F. Byrne, his creation dating back to 1918. For years, he had tried to get the interest of the U.S. Government in his cipher system but failed. Later on, his son, John Byrne, picked up from where his father left, added some improvements and provided additional information with the help of two Cryptologia editors, the Chaocipher finally became a challenge to would-be solvers.

The seven gold bars issued to a General Wang in Shanghai in 1933 appear to represent metal certificates related to a bank deposit with a U.S. bank, presenting pictures, Chinese writing, some form of script writing and cryptograms in Latin letters. Although the Chinese writing has been translated, discussing a transaction in excess of $300,000,000, the gold bars themselves weighing a total of 1.8 kg, no one has managed to crack the other codes on the bars.

The Shepherd’s Monument at Shugborough Hall is actually a relief depicting a woman watching three sheperds pointing to a tomb, where the Latin text “Et in arcadia ego” (“I am also in Arcadia/I am even in Arcadia”) is written. Based on the French artist Nicholas Poussin’s painting, the relief presents some changes, the more obvious being the fact that it is reversed horizontally. The fact that one of the shepherds in the relief is pointing to the letter N in the word IN is another mystery, together with another change that differentiates the relief from the original painting, the former presenting an extra sarcophagus to the scene. Below the image of the monument are the following letters: D O .U .O .S .V .A .V .V . M which for the modern Grail-conspiracy believers holds a clue to the actual location of the hidden or lost Holy Grail. Could that be so? So far, no one has managed to decipher the code.

A sculpture by the American artist James Sanborn, Kryptos is located in the grounds of the CIA in Langley, Virgina US, as a dedication on November 3rd 1990. Most of the characters have been deciphered (768 of 869 or 970-as Sanborn officially stated that an intended letter was missing), nevertheless, the Kryptos continues to provide a diversion for the CIA employees and cryptanalysts on the remaining 97 or 98 characters.

D’agapeyeff cipher is a “challenge cipher” appearing at the end of an elementary book on cryptography published by Alexander D’Agapeyeff, a Russian-born English cryptographer, in 1939. It is said that he himself forgot how he had encrypted it, and that the cipher is undecipherable because D’Agapeyeff encrypted it incorrectly. Nevertheless, there are some who claim that the cipher can be broken using computational methods, such as genetic algorithms.