Texas Instruments aims lawyers at calculator hackers

Copyright or control?

Another issue clouding the case is whether TI is using the DMCA to protect copyrighted material or merely to control the way its calculators are being used by people who legally own them, said Jennifer Granick, an attorney for the Electronic Frontier Foundation.

"If they're using the DMCA to control the platform rather than to prevent infringement, the courts and the Copyright Office have looked askance at that in the past," said Granick, who was responsible for winning the copyright exemption for unlocking cell phones so they can be used on unauthorized carrier networks. "Users have the right to modify their own devices and their own copies of software to make it work best for them."

Asked what the precise copyright issue was in the DMCA takedown demands, a company spokeswoman said: "TI's graphing calculator software is copyrighted material. In an effort to protect our intellectual property we have sent these notices." She didn't elaborate.

In all, the hobbyists have published 14 private keys used to digitally sign firmware that runs a wide variety of calculators, including the TI-73, TI-83 Plus, TI-84 Plus models. OSes that don't bear the signature will fail to work unless users carry out other, more cumbersome hacks. The private keys were derived by reverse engineering the hardware to discover its public key and then using a series of computing-intensive mathematical factoring operations.

Thirteen of the keys were cracked by 500 networked computers that sieved some 12.5 512-bit integers over a four-week stretch, according to this post by Lionel Debroux, who helped spearhead the project. The 13th integer had to be sieved manually. The project would have been impractical had the keys used more bits.

Despite TI's efforts to keep the keys out of the public limelight, many of them remained available here on the Wikileaks site.

Both Smith and Wilson insist the goal from the start has been to allow them to run customized firmware on their legally purchased calculators. They say TI is using copyright concerns as a red herring to conceal its real motive, which is to prevent the devices from being disqualified in classrooms while tests are being administered.

"TI has the educational market squarely nailed down and they don't have anything to worry about so long as they make sure their calculators can be trusted to be resettable," Smith told The Register. "They've got all the (test) administrators knowing the TI calculators are trustworthy, and they don't want that to be undermined."

TI's website here shows that many of the OSes haven't been updated in years.

Said Wilson: "Their lack of updates and attention to the series is only more motivation for us to come up with our own solution for an operating system." ®