The 340 cipher that took 51 years to crack — and still named no killer

The 340 cipher sat unsolved for fifty-one years.

On December 5, 2020, a team of codebreakers—David Oranchak, Sam Blake, and Jarl Van Eycke—announced they had deciphered it.

The decoded message read as a confession of sorts, a taunt about collecting slaves for the afterlife.

It contained no name.

It named no accomplice, no address, no date.

The solution produced no suspect.

That is the anticlimax at the heart of the most famous unsolved crime in American history.

The case began on December 20, 1968, with the murders of two teenagers on a secluded road in Benicia, California, near Vallejo.

They were shot dead while parked, a young couple on a first date.

There were no witnesses.

There was no confession.

There was only a killer who, months later, began writing letters.

He sent a series of taunting, cryptogram-laden letters to newspapers, coining the name "Zodiac" and claiming responsibility.

He wrote in code.

He wrote in riddles.

He wrote as if he wanted to be caught—and then made sure he never was.

The first cipher, the "408," was solved by a schoolteacher and his wife in 1969.

It contained no identity either.

The second, the "340," took half a century.

Why so long?

Why did three codebreakers succeed where decades of investigators had failed?

The answer is in the method, not the message.

The cipher was not a simple substitution; it was a transposition, a grid that needed to be rearranged before it could be read.

Oranchak and his team found that by reading the columns diagonally, the letters fell into place.

The text that emerged was rambling, boastful, and empty.

It is a document of ego, not evidence.

The identity of the killer is not established by the record.

The cipher's solution produced no suspect.

That is what the record shows.

That is all the record shows.

THE FIRST REPORTS

The first attack came on December 20, 1968.

Two teenagers were shot on a secluded road in Benicia, California, near Vallejo.

Both died.

The weapons were a .22-caliber pistol in the first two attacks, a knife at Lake Berryessa, a 9mm at the taxi.

On July 4, 1969, two people were shot in a parked car at Blue Rock Springs Park in Vallejo.

One died, one survived.

The killer's identity was not established.

On September 27, 1969, two people were stabbed at Lake Berryessa.

One died, one survived.

Four months later, on October 11, 1969, a taxi driver was shot and killed in San Francisco's Presidio Heights.

The attacks escalated in frequency.

They escalated in brutality.

The first was a shooting.

The second was a shooting.