The operator of the cryptocurrency mixing service Helix was sentenced to three years in prison on Friday.

Akron, Ohio native Larry Dean Harmon, 41, pleaded guilty in 2021 to conspiracy to commit money laundering. A Justice Department spokesperson did not respond to requests for comment about why the sentencing took place three years after the deal was agreed to.  

It is unclear whether Harmon will be released this year. In addition to his term in prison, Harmon was sentenced to three years of supervised release and has to forfeit more than $311 million as well as seized cryptocurrencies, real estate, and monetary assets valued at over $400 million.

From 2014 to 2017, Harmon ran Helix, facilitating more than $300 million worth of cryptocurrency transactions. 

The platform helped cybercriminals launder their Bitcoin and was connected to a darknet search engine called Grams, which was also run by Harmon. 

Tumbling or mixing services like Helix typically charge a fee to pool together large amounts of funds from various owners, then "mix" the funds together and distribute them back out to destination addresses, which makes it difficult to trace digital coins to their original owners.

According to the Justice Department, Helix was particularly popular among online drug dealers seeking to launder the proceeds of narcotics sales, processing a total of 354,468 bitcoin, worth $311 million at the time of the transactions. 

Harmon earned a profit by taking a percentage of the transactions as a fee. 

The platform grew in popularity because Harmon was able to connect it to other darknet markets — including AlphaBay, Cloud 9, and Evolution — making it an easy financial off-ramp for cybercriminals and drug operations. 

The investigation was conducted by several U.S. agencies as well as law enforcement officials in Belize. The Financial Crimes Enforcement Network previously levied a $60 million civil penalty against Harmon. 

Harmon faced up to 20 years in prison under the original charges. His brother Gary Harmon was sentenced to more than four years in prison last year for stealing bitcoin his brother’s operation had generated. The younger Harmon was sentenced to four years in prison for attempting to access accounts that had already been seized by the FBI. 

Law enforcement agencies are in a near constant game of whack-a-mole with these types of mixing services — issuing dozens of sanctions over the last five years against popular cybercriminal tools like Tornado Cash, Sinbad and its predecessor Blender.io, ChipMixer, and most recently Samourai Wallet and Bitcoin Fog. 

Roman Sterlingov, the Russian and Swedish operator of Bitcoin Fog, was sentenced last week to 12 years in U.S. prison.