HID claimed that Paget's talk would infringe upon two patents the company owns, one and another . Both cover methods of detecting RFID signals between a transponder embedded in a device and an "interrogator," according to a source familiar with HID's claims.

Pennell and others doubted that such broad patent claims could be used to stifle free speech, but said that the legal pressure mounted by HID, a subsidiary of Swedish firm ASSA ABLOY, was too much for his small, Seattle-based consulting firm to withstand.

"If we say anything, HID will sue. These large companies have lots of resources, so they can find [legal] matter with pretty much anything," Pennell said, admitting disappointment at the failure to reach an agreement with HID.

"It's always been IOActive's intent to help people with security," he said.

Chris Paget said that, unlike Lynn's sophisticated hack of Cisco's IOS operating system, the RFID cloning devices he built were simple devices concocted from around US$20 in off-the-shelf parts purchased on eBay.