Video posted on YouTube by Virginia web-designer David Oranchak says he cracked the cipher along with Australian applied mathematician Sam Blake and Belgian Jarl Van Eycke, a warehouse manager and code-breaking software engineer. The unidentified killer infamously sent the mediafour ciphers, or cryptograms, which are a type of puzzle.
"On Dec. 5, the Federal Bureau of Investigation received the solution to a cipher popularly known as Z340 from a cryptologic researcher and independently verified the decryption", the Federal Bureau of Investigation said in a statement.
"We have been sitting in the settlement since last Saturday", he said.
When I first started looking at the Zodiac ciphers all those years ago, I thought, 'Oh, I can just write a computer program and solve it, ' but it's been kicking my a** all this time.
The "Z-340" message - coined that as it contained 340 characters, a mix of letters and symbols - was first sent to the San Francisco Chronicle in November 1969, amid of string of ciphers, threatening letters and evidence (swatches of a victim's shirt) that the Zodiac Killer sent to the newspaper.
'I am not afraid of the gas chamber because it will send me to paradice (sic) all the sooner because I now have enough slaves to work for me. He claims he killed as many as 37 people.
Dr Blake got interested in the Zodiac's riddles after seeing online videos from US cryptologist David Oranchak who has been trying to crack the code for 15 years.
Investigators had hoped the cipher would reveal the killer's name, but the message did not mention it.
Until now, one of the coded messages, which was sent to the San Francisco Chronicle in 1968, has never been cracked. No murder has been officially linked to the Zodiac Killer since October 1969, but the unsolved case continues to fascinate.
The TV show that the killer was referring to was "The Jim Dunbar Show". "Due to the ongoing nature of the investigation, and out of respect for the victims and their families, we will not provide further comments at this time". However, even though the letter has been deciphered, it does not contain any identifiable information that could point towards the killer.
"The cipher was recently resolved by a team of three private citizens".
In the message, the killer was, in a way, making fun of the receiver for not being able to catch him.