Bitcoin's blockchain is public and transparent, showing all transactions since the system was launched. But following the flow of bitcoins can get tricky, especially if "mixing" services are used, which create spider web-like transaction trails.
Gavin Andresen, chief scientist for the Bitcoin Foundation, said the FBI likely has deeper information on the Silk Road's transactions, some of which may not have been illegal.
"If I was an evil mastermind designing a bitcoin mixing service, I would certainly try to mix in perfectly innocent bitcoin transactions to try to hide the illegal activity," he wrote in an email.
Shamir said he and Ron followed well-established approaches in social science research for describing correlations, clearly stating "what is a scientific fact and what is an unproven conjecture."
But controversy over those last four paragraphs unfortunately undermined one of the paper's most interesting conclusions: that the FBI has only seized about 22 percent of the 633,000 or so bitcoins the Silk Road collected in commissions from facilitating contraband sales.
In his email, Shamir said bitcoin enthusiasts do not like analyses that do "not fully support their beliefs." He also took a swipe at the media.
"It was the media reporting, and not our paper, which made this side issue a cornerstone of our paper," he wrote.
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