Why was the Black Hat talk on Tor de-anonymization mysteriously canceled?

Researchers from the CERT division of Software Engineer Institute (SEI) at Carnegie Mellon University, which "works closely with the Department of Homeland Security," were set to give a talk purporting to demonstrate a way to deanonymize Tor users at Black Hat USA, a major cybersecurity conference, in early August. Alexander Volynkin and Michael McCord, both researchers at CMU, were slated to disclose a method for identifying Tor users and services with "newly discovered shortcomings in design and implementation of the Tor network," an abstract for the talk said, that only cost $3,000 or so to exploit.
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