© Getty Images

The McCormick Cipher -

The body of 41-year-old Ricky McCormick was discovered in June 1999, in Missouri. The police found two encrypted notes in his pockets. This didn't raise any alarm bells as McCormick was known to have written code and his death was not considered suspicious. 

© Public Domain

The McCormick Cipher -

Until it was. Unable to crack the complex code, which consisted of letters, numbers, and symbols, the FBI believed that McCormick had been murdered. They came forward and even asked for help from members of the public, but to no avail. To this day, no one has been able to decipher it. 

© Public Domain

Tamám Shud -

In December 1948, a note was found in the pocket of a dead man at Somerton Park beach in Adelaide, Australia. To this day no one has been able to identify who the man was. He became known as the Somerton Man.

© Public Domain

Tamám Shud -

In his pocket, the police found a paper which read "Tamám Shud," which means "Ended," or "Finished" in Persian.  

© Public Domain

Tamám Shud -

The piece of paper was from a book titled 'The Rubaiyat of Omar Khayyam,' which was found in a car, near a location Somerton Man supposedly visited before being murdered. On the back of the book was a cipher, that to this day hasn't been cracked. The case remains unsolved.

© Public Domain

Beale Ciphers -

The Beale Ciphers was a pamphlet published in Virginia in 1885. It contained the story of a man named Beale and it had three encrypted messages.

© Public Domain

Beale Ciphers -

The story goes that Beale buried a treasure somewhere in Bedford County, Virginia. This was the information in one of the ciphers, which was decoded. As for the other two, they are said to contain the exact location of the treasure, but so far no one was able to crack the code. 

© Shutterstock

The Rohonc Codex -

Discovered in Hungary in the early 19th century, the Rohonc Codex is believed to date back to the Middle Ages. The author of the illustrated manuscript is unknown. While its script resembles Old Hungarian, it remains indecipherable.

© Public Domain

The Rohonc Codex -

The Rohonc Codex appears to be a religious text, because it contains Christian, Muslim, and pagan iconography. Many scholars however believe it to be a hoax from the 18th century. Either way, no one really know what's written in the Codex.

© Public Domain

The Indus aka Harappan Script -

Back in 1875, script of the Indus civilization was discovered in numerous artifacts in the area where Mesopotamia used to be. The Indus Valley civilization date back to around 4,500 years ago.

© Public Domain

The Indus aka Harappan Script -

About 500 Indus symbols were identified. Some scholars believed the script to be some sort of primitive language. But to this date, no one really knows what they mean. 

© Getty Images

Kryptos -

Kryptos is a sculpture by artist James Sanborn, made with the collaboration of former Central Intelligence Agency (CIA) cryptographer Ed Scheidt in 1990. It can be found on the grounds of the CIA in Langley, Virginia. It contains an encrypted message divided into four sections.

© Getty Images

Kryptos -

Three sections were deciphered by computer scientist James Gillogly in 1999, though the fourth section, which is known as the K4, has yet to be cracked.

© Getty Images

The Dorabella Cipher -

In 1827, English composer Edward Elgar sent a letter to his friend, Dora Penny. But this was no ordinary letter—its message was enciphered. 

© Public Domain

The Dorabella Cipher -

The letter contained a cipher with 87 characters. It has been speculated that it was a private code shared between the two friends, but to date no one has been able to decipher it. 

© Public Domain

Shugborough Hall Inscription -

The Shepherd's Monument can be found in the grounds of Shugborough Hall in Staffordshire, England.

© Getty Images

Shugborough Hall Inscription -

It's believed to have been built sometime between 1748 and 1763, and it contains a mysterious message at the bottom that reads "D O.U.O.S.V.A.V.V. M."

© Public Domain

Shugborough Hall Inscription -

Various theories have been put forward, including that it holds a clue to the location of the Holy Grail, but to this day, no one really knows what it means. 

© Public Domain

Linear A -

The Minoan civilization, who called Crete and other Aegean islands home around 2000 BCE, are credited with developing one of (if not the) first written systems in Europe. Namely, Cretan Hieroglyphs and Linear A.

© Public Domain

Linear A -

Discovered by archaeologist Sir Arthur Evans, Linear A contains about 90 symbols, which are yet to be deciphered. 

© Getty Images

Voynich Manuscript -

Discovered by rare-book dealer Wilfrid Voynich in 1912, the Voynich Manuscript is believed to date back to sometime between 1404 and 1438. 

© Public Domain

Voynich Manuscript -

In its 240 pages, the Voynich Manuscript has numerous illustrations and diagrams, organized into various sections, from herbs to biology, among others.  

© Getty Images

Voynich Manuscript -

The author and the language it's written in remains unknown. Cryptographers have tried to decipher it ever since, but to no avail.  

© Public Domain

The Phaistos Disc -

The Phaistos Disc was discovered by archaeologist Luigi Pernier in 1908 in Phaistos, Crete. It's believed to date back to the Minoan Bronze Age. The disc contains a spiral of symbols on both sides.

© Getty Images

The Phaistos Disc -

Many have attempted to decipher the code over the years, but no one has been able to do so. 

© Getty Images

Rongorongo -

Rongorongo is a system of glyphs discovered in a number of tablets back in the 19th century on Easter Island. 

© Public Domain

Rongorongo -

It goes without saying that attempts to decode the inscriptions were unsuccessful. 

© Public Domain

Cicada 3301 -

Cicada 3301 is actually a nickname given to an entity. They are known for having posted three sets of puzzles online between 2012 and 2014.

© Shutterstock

Cicada 3301 -

While the first two rounds of puzzles have been deciphered, the third one is still a mystery. 

Sources: (The Richest) (New Scientist) (Rank Red) (Mentalfloss)

See also: How to protect your digital privacy

© Shutterstock