Today, on day 11 of the Tornado Cash trial, Dr. Edman, co-founder and partner at Naxo, a digital forensics and investigations firm, took the stand for the majority of the trial day.
In his direct testimony, he defined key crypto terms for the court, explained the extent to which Tornado Cash was decentralized, highlighted the precautions Roman Storm and the other Tornado Cash co-founders took to prevent bad actors from using the service, and called into question the validity of the analysis presented by two former witnesses.
During the cross-examination, the prosecution prodded Dr. Edman to share details and to provide nuance regarding some of the claims he made and the data he presented in his testimony.
Describing How Tornado Cash Works
In his slides, Dr. Edman described Tornado Cash as a noncustodial service that used immutable smart contracts to anonymize transactions.
As he introduced crypto-specific words and phrases that might have been unfamiliar to the jury such as “cryptographic signatures,” “smart contracts,” and the aforementioned “immutable,” he defined them in layperson’s terms.
He was so thorough in doing so that his efforts became seemingly counterproductive in that he lost some of the members of the jury in the process.
That said, he did make a number of notable points in his testimony, including that the Tornado Cash pool contracts had been immutable since May 18, 2020, that the Tornado Cash DAO played a role in governing Tornado Cash (as opposed to just Storm and his co-founders), and that a “minified” (reduced) version of the source Tornado Cash user interface (UI) source code had existed on GitHub since nearly the onset of the project for the technically inclined to copy and use as they pleased.
Dr. Edman also noted that even the UI for Tornado Cash was decentralized in a sense in that it existed on IPFS (InterPlanetary File System), a peer–to-peer storage system for sharing data across distributed networks.
The Precautions The Tornado Cash Developers Took
Dr. Edman highlighted the fact that Storm and his co-founders applied a geoblocking system to the UI, making it more difficult for people or entities from certain regions of the globe, like North Korea or Cuba, to use the UI.
He also noted that the Tornado Cash developers implemented the Chainalysis Sanctions Oracle — a smart contract that includes a list of sanctioned addresses — within a month of Chainalysis’ creating the tool.
Criticizing The Testimony of Two Other Witnesses
Dr. Edman stated that he’d reviewed the data that FBI Special Agent DeCapua presented last week, while pointing out that the wallets associated with the Ronin hack didn’t move funds through Tornado Cash. He said that there were a number of hops from the Ronin hack wallet to Tornado Cash, making the analysis harder to validate.
He added that from September 1, 2020 to August 8, 2022, 85% of funds that moved through Tornado Cash were “unidentified” while only 13% were from hacks from DeCapua’s demonstrations, making the point that the majority of Tornado Cash users weren’t necessarily criminals.
Dr. Edman also critiqued the testimony from Philip Werlau, a blockchain auditor from AnChain.AI and a witness for the prosecution.
Dr. Edman was particularly critical of Mr. Werlau’s unique “gas ratio analysis,” which tracked crypto deposits into Tornado Cash. He stated that he doesn’t know of this methodology’s known error rates and that neither did Mr. Werlau. (He said as much in his testimony.)
Cross-Examining Dr. Edman
Toward the beginning Dr. Edman’s cross-examination, the prosecution harped on the fact that, from December 2020 until August 8, 2022, almost all of the funds that moved through Tornado Cash were put through a router that Storm and his co-founders had set up.
The prosecution showed a slide illustrating Tornado Cash’s 7,764 deposits and 7,322 withdrawals for the 100 ETH Tornado Cash pool via the router in February 2022, a month in which no funds were processed through said pool directly.
While Dr. Edman largely agreed with this being the case, he didn’t support the prosecution’s claim that the criminals were moving illicit funds through the router because doing so helped them to increase their anonymity. (The prosecution argued that the criminals’ putting the funds through the same entry point as all of the other users helped to make the transactions not stand out.)
Also during the cross-examination, the prosecution stated that the owners of the Tornado Cash organization’s GitHub account (Storm and his two co-founders) made the final decisions regarding what was included in the UI and they added that the source code for the UI wasn’t as open source as Dr. Edman claimed it was during his testimony.
To the latter point, the prosecution argued that only providing the minified source code wasn’t the same as providing the full source code.
Dr. Edman was reluctant to agree with this assessment, and settled by stating that under the strict definition of open source the prosecution provided, the Tornado Cash UI wasn’t technically fully open source from the onset.
The prosecution also asked Dr. Edman whether Storm and the other Tornado Cash developers actually incorporated the geoblocking code.
They showed a commit for the code that Dr. Edman had included in his slides, and pressured Dr. Edman to share whether or not he knew for sure the code was merged. Dr. Edman said that it was to the best of his knowledge.
A Second Witness Takes The Stand
With approximately 10 minutes left in the trial day, the defense called their second witness of the day, Tyler Alameida, to the stand.
Mr. Alameida works in cybersecurity at Coinbase and testified to the fact that he once used Tornado Cash to preserve his privacy as he sent funds from his wallet to the Ukrainian war fund.
While Judge Failla hadn’t allowed much space for the witnesses to talk about the privacy use case for Tornado Cash, she did permit Mr. Alameida to tell his story within the just over five minutes he was on the stand.
What’s Next?
The defense will call more witnesses to the stand tomorrow, one of which will be a custodian for Chainalysis.
After that the defense has stated that it plans to bring approximately four more witnesses to the stand, including potentially Roman Storm himself.