Ten Codes and Ciphers Nobody Has Cracked

In 1912 the rare-book dealer Wilfrid Voynich bought a strange little volume from a Jesuit college at Frascati, near Rome. Every page is written in a flowing script that matches no known language, alongside drawings of plants nobody can identify, astronomical diagrams, and scenes of figures bathing in pools. It now sits at Yale's Beinecke Rare Book and Manuscript Library as MS 408, donated in 1969 by the dealer H. P. Kraus.

The library groups the pages into six kinds of material: botanical, astronomical and astrological, bathing scenes, cosmological medallions, pharmaceutical drawings of roots and herbs, and dense text that may be recipes. Radiocarbon testing dated the vellum to between 1404 and 1438, and ink analysis is consistent with a 15th-century book.

That dating hurt one popular theory, that a later forger produced it with a 16th-century trick for generating fake text. A later statistical study published in PLoS One argued the word patterns behave like real language, with keyword clusters tied to particular sections. Yet every proposed translation, from lost dialects to shorthand Latin, has collapsed under scrutiny. Linguists, codebreakers and, more recently, computer models have all taken turns. Nobody can yet read a single sentence with confidence.

The Zodiac Killer, who terrorized Northern California in the late 1960s, mailed four ciphers to newspapers and police. Two have been broken. A Salinas schoolteacher couple, Donald and Bettye Harden, cracked the 408-character cipher within about a week in 1969. The 340-character cipher held out for 51 years until December 2020, when David Oranchak, Sam Blake and Jarl Van Eycke solved it with heavy computer help, and the FBI confirmed their result.

The other two remain open. The first, known as Z13, arrived on April 20, 1970: just 13 symbols, introduced by the words "My name is." That framing made it irresistible, but 13 characters is far too short to solve with any certainty, and hundreds of names can be forced to fit.

Z32 followed on June 26, 1970, with a map of the Bay Area and a compass drawn around Mount Diablo. A follow-up letter in July hinted that the code concerned radians and inches measured along them. With only 32 characters and an unknown method, it is almost as intractable as Z13. The Zodiac case is still an open investigation, and so are both short ciphers.

Before he was famous, the English composer Edward Elgar had a fondness for puzzles. On July 14, 1897, he tucked a short coded note into a thank-you letter his wife sent to Dora Penny, a 23-year-old friend he nicknamed Dorabella. It consisted of 87 small curly symbols spread unevenly across three lines.

Dora could not read it. She put it away in a drawer and did not take it out for about 40 years, finally publishing a copy in her 1937 memoir about Elgar. By then she had another claim to fame: Elgar had portrayed her in one movement of his Enigma Variations, which premiered in 1899 and made his name.

The cipher uses 24 distinct shapes, which suggests a simple substitution alphabet, yet no straightforward substitution yields sensible English. Proposed solutions range from personal messages to hidden music to deliberate nonsense, and critics point out that some claimed decryptions spell out the nickname Dorabella, which Elgar apparently did not use until 1898. A 2007 Elgar Society competition ended without a winning solution. The note may be a private joke whose meaning depended on context only two people ever had.

On the morning of December 1, 1948, a well-dressed man was found dead against a seawall on Somerton beach near Adelaide. His clothing labels had been removed, he carried no identification, and tests for common poisons came back negative. In a hidden pocket, investigators found a tiny scrap of paper printed with the words "Tamám Shud," torn from the last page of a copy of the Rubaiyat of Omar Khayyam.

In July 1949 a local man brought police the matching book, which he said he had found in a car parked near the beach. On the back cover, under ultraviolet light, police found five lines of jumbled capital letters, the second line crossed out. Naval Intelligence studied them and concluded there were too few letters for a firm answer; it suggested they might be the first letters of words in a verse. Countless amateurs have tried since.

In 2022, University of Adelaide professor Derek Abbott and genealogist Colleen Fitzpatrick announced, based on DNA from hair in a plaster death mask, that the man was Carl "Charles" Webb, a Melbourne electrical engineer. South Australian authorities had not formally confirmed it as of mid-2026. Even with a name, the letters in the book remain unread.

On June 30, 1999, the body of Ricky McCormick, 41, was found in a field outside St. Louis. Investigators believed he had been killed somewhere else and left there. In his pants pockets were two handwritten notes made up entirely of capital letters, numbers, dashes and parentheses, more than 30 lines in all. The FBI believes he wrote them up to three days before his death.

For more than a decade the bureau's Cryptanalysis and Racketeering Records Unit, which specializes in coded messages from criminals and spies, worked on the notes without success. In March 2011 it did something unusual: it published images of both pages and asked the public for help. The unit's chief admitted the cipher system was one his team knew nothing about.

One possibility is that the notes are not a formal cipher at all but a personal shorthand of abbreviations, which would be nearly impossible to read without knowing the writer's habits. Whatever they are, no accepted solution has emerged, and his killer has not been caught. The notes may hold a clue to his killer, or nothing more than a grocery list.

The Rohonc Codex is a pocket-sized book of 448 paper pages, each about 4.7 by 3.9 inches, filled with rows of symbols in a script nobody recognizes. It also contains 87 illustrations of religious, secular and military scenes. It was kept at Rohonc until 1838, when Count Gusztáv Batthyány donated it, along with his entire library, to the Hungarian Academy of Sciences.

Its script is the core puzzle. Scholars have counted roughly 800 distinct symbols, about ten times more than any alphabet, which suggests a syllabary, a set of word signs, or something artificial. The paper appears to be Venetian, probably from the 1530s, though the text could have been written later or copied from an older source.

Readings have been proposed as a Sumerian-like script, a Latin dialect of medieval Romania, and a variant of India's Brahmi script, and critics have rejected each. In 2018, Hungarian researchers Gábor Tokai and Levente Zoltán Király argued it is an invented code system recording a Catholic devotional text paraphrasing the New Testament, possibly written around 1593. Since 1866 some Hungarian scholars have suspected the 19th-century forger Sámuel Literáti Nemes, though no direct evidence ties him to it. No reading has won general acceptance.

On the grounds of Shugborough Hall, an English country estate, stands the Shepherd's Monument, commissioned by Thomas Anson sometime between 1748 and 1763. Its centerpiece is a carved relief adapted from Nicolas Poussin's painting The Shepherds of Arcadia. Below it are ten letters: OUOSVAVV, flanked by a D and an M.

The D and M are the easy part. On Roman tombs, they stand for Dis Manibus, a dedication to the spirits of the dead. The eight letters between them are the mystery. Charles Dickens and Charles Darwin are said to have puzzled over them, and theories range from a coded love letter to a Bible verse to, inevitably, a pointer to the Holy Grail.

Some proposals come from serious people. Sheila Lawn, a veteran codebreaker from Bletchley Park, suggested the letters are initials of a Latin love message. Keith Massey, a Latin teacher who reportedly worked for the NSA, read them as initials of a Latin phrase echoing John 14:6. Historian A. J. Morton argued instead that the letters may be little more than early 19th-century graffiti added by relatives of the Anson family. Eight letters is far too few to prove any of these right, and so the inscription keeps its secret.

Most unbroken ciphers come from murderers, spies or eccentrics. This one comes from a textbook. In 1939, Alexander D'Agapeyeff, a Russian-born cartographer and writer living in England, published Codes and Ciphers, a popular introduction to cryptography from Oxford University Press. On the last page he printed a short block of digits and invited readers to test their skill on it.

It is meant to be an exercise, so it should be breakable. It is not, or at least nobody has managed it. The numbers are usually read in pairs, which hints at a grid-based substitution like the Polybius square D'Agapeyeff explains earlier in the book, possibly combined with a transposition. Cryptographers have tested those methods and many others without producing readable text.

That has led to an awkward theory: the author may have made a mistake when he enciphered it, so the puzzle has no clean solution. A widely repeated story says he later admitted forgetting how he built it, but we could not find a primary source for that claim. The German cryptology writer Klaus Schmeh lists it among the best-known unsolved cryptograms, and it has been posted as an open challenge on puzzle sites. For now, the textbook's final exam has beaten every student.

Since November 1990, a copper sculpture called Kryptos by the artist Jim Sanborn has stood in a courtyard at CIA headquarters. It holds four encrypted passages. The first three, K1 to K3, were solved in the 1990s by an NSA team, a CIA analyst working by hand, and California cryptographer Jim Gillogly. The fourth, a 97-character passage called K4, has defeated everyone. Sanborn released clues over the years: BERLIN in 2010, CLOCK in 2014, NORTHEAST and EAST in 2020.

In 2025 the story took a strange turn. Sanborn, nearing 80, announced he would auction the solution. That September two writers, Jarett Kobek and Richard Byrne, found scraps of the plaintext that Sanborn had accidentally left in papers he gave to the Smithsonian's Archives of American Art. Sanborn insisted they had found the answer, not cracked the cipher or its key. The Smithsonian sealed the materials, and the pair did not publish what they read.

In November 2025 his archive sold at RR Auction in Boston for about $963,000 to an anonymous buyer. In 2026 the crypto investment firm Paradigm revealed itself as the owner. It says it locked Sanborn's answer in an automated verifier without ever viewing it and charges $1 per guess. As of October 2026, nobody has publicly solved K4 by cryptanalysis.