TI's calculators perform a "signature check" that allows only approved operating systems to be loaded onto the hardware. But researchers were able to reverse-engineer signing keys, allowing tinkers to install custom operating systems and unlock new functionality in the calculators' hardware. In response to this discovery, TI unleashed a torrent of demand letters claiming that the anti-circumvention provisions of the Digital Millennium Copyright Act (DMCA) required the hobbyists to take down commentary about and links to the keys. EFF represents three men who received such letters.
"The DMCA should not be abused to censor online discussion by people who are behaving perfectly legally," said Tom Cross, who blogs at memestreams.net. "It's legal to engage in reverse engineering, and its legal to talk about reverse engineering."