The head of the Tor Project has accused the FBI of paying Carnegie Mellon computer security researchers at least $1 million to de-anonymize Tor users and reveal their IP addresses as part of a large criminal investigation.

Neither Carnegie Mellon officials nor the FBI immediately responded to Ars' request for comment. If true, it would represent a highly unusual collaboration between computer security researchers and federal authorities.

Ed Desautels, a spokesman for Carnegie Mellon’s Software Engineering Institute, did not deny the accusations directly but told Wired: “I’d like to see the substantiation for their claim,” adding, “I’m not aware of any payment.”

One of the IP addresses revealed belongs to Brian Farrell, an alleged Silk Road 2 lieutenant who is due to stand trial in federal court in Seattle later this month. A new filing in Farrell's case, which was first reported Wednesday by Vice Motherboard, says that a "university-based research institute" aided government efforts to unmask Farrell.

As Ars reported in January 2015, a Homeland Security search warrant affidavit states that from January to July 2014, a “source of information” provided law enforcement “with particular IP addresses” that had accessed the vendor-side of Silk Road 2.

By July, the Tor Project managed to discover and shut down this sustained attack. The Tor Project further concluded that the attack resembled a technique described by a team of Carnegie Mellon University researchers who a few weeks earlier had canceled a security conference presentation on a low-cost way to deanonymize Tor users. The Tor officials went on to warn that an intelligence agency from a global adversary also might have been able to capitalize on the vulnerability.

In a blog post published Wednesday, Tor Project Director Roger Dingledine said there is "no indication yet that [federal authorities] had a warrant or any institutional oversight by Carnegie Mellon's Institutional Review Board."

Dingledine did not immediately respond to Ars' request for proof of this $1 million payment allegation.

He continued: