Graphing calculators have long inspired geeks in remarkable ways. But, sadly, rather than celebrating the hobbyists that love their programmable calculators, Texas Instruments has set the lawyers loose on them, invoking the Digital Millennium Copyright Act (DMCA).

The story is a familiar one: hobbyists started tinkering with their calculators, intent on improving them, much like gearheads have been doing with cars for generations. But TI’s programmable graphing calculators perform a signature check that only allows a signed operating system to be loaded onto the hardware. That didn't stop our intrepid tinkers, however. Researchers used distributed computing to perform a brute-force cryptanalysis of the public keys embedded in each model of calculator to derive the corresponding private keys. (When the keys were discovered, people in the programmer community were excited. Some saw this as the first real world example of "angry mob cryptanalysis," an attack by a bunch of people getting together on the Internet to crack your key.)

With the key, calculator owners can install their own homebrew operating system that unlocks new functionality in the hardware. There's long been a devoted hobbyist community writing OS code and a repository of alternative operating systems on the web. The cracked keys allow for easy and elegant use of this code.

In other words, in the best traditions of tinkers everywhere, these hobbyists took their tools and made them better.

TI’s response has been to target programmers and bloggers with cease and desist letters telling them that the anti-circumvention provisions of the Digital Millennium Copyright Act require them to take down the keys, remove links to forum discussions, and delete blog posts.

The law, however, is not on TI's side. Courts have repeatedly rejected attempts to use the DMCA to control owners’ use of embedded software in the devices they buy.

The DMCA prohibits circumvention of DRM or other technological measures that control access to, or copying of, copyrighted works, as well as distribution of circumvention tools. But owners of TI calculators already have unlimited access to the TI operating system and bootrom code that comes installed on their calculators. They can run the code on their calculators or just download it from the TI website. The software is not encrypted or otherwise locked up (unlike the firmware on Apple's iPhone, which is encrypted, which is why we're seeking a DMCA exemption for iPhone jailbreaking). And that means that the signing key does not "control access" within the meaning of the DMCA. In the words of the court in Lexmark v. Static Controls (where Lexmark tried to use the DMCA to stop refills of laser printer toner cartridges):

Just as one would not say that a lock on the back door of a house "controls access" to a house where the front door does not contain a lock and just as one would not say that a lock on any door of a house "controls access" to the house after a purchaser receives the key to the lock, it does not make sense to say that this provision of the DMCA applies to otherwise-readily-accessible copyrighted works.

And TI's DMCA claim fails for another reason, as well: running software of your choice on your calculator has no "nexus" with copyright infringement. The courts have made it clear (1, 2) that you need a nexus with infringement if you want your DMCA claim to stick. This is not about decrypting copyrighted code so that you can distribute it to the four corners of the Internet. This is about running your own software on your own calculator. So where's the copyright infringement in that?

That's two fatal flaws in TI's DMCA arguments, without even considering the explicit exemption in the statute (Section 1201(f)) for reverse engineering in order to create interoperable software (like homebrew operating systems for your calculator).

It looks like TI is following in the footsteps of Apple, sending baseless legal threats that invoke the DMCA. This strategy could end up alienating the most committed TI customers, and selling fewer calculators.

UPDATE: EFF sent TI a letter October 13th, warning the company not to pursue its baseless legal threats.