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A TI-83+ graphing calculator

The Texas Instruments signing key controversy refers to the controversy which resulted from Texas Instruments' (TI) response to a project to reverse engineer the 512-bit RSA cryptographic keys needed to write custom firmware to TI devices.[1]


In 2009, a group of hackers used brute force and distributed methods to find all of the cryptographic signing keys for a variety of Texas Instruments calculators, allowing users to flash their own operating systems directly to the devices.[2] The key for the TI-83+ calculator was first published by a United-TI forum user, who needed several months to crack it. The other keys were found after a few weeks by the TI calculator community through a distributed computing project.

Legal response[]

Texas Instruments began by sending out two initial DMCA take-down requests to the hackers, referring to sites or forum posts that they controlled.[3][4] The hackers responded by removing the keys, without consulting an attorney.[5] TI then sent further DMCA notices to a variety[6] of different websites displaying the keys, including United-TI, reddit, and Wikipedia. Texas Instruments' efforts then became subject to the Streisand effect,[7] and the keys were mirrored on a number of different sites, including Wikileaks and WordPress. In September 2009, Dan Goodin from The Register alerted the Electronic Frontier Foundation (EFF) to TI's actions, and the EFF agreed to take on the case, representing three people who had received DMCA notices. On October 13, 2009, the EFF sent a letter to TI warning them that the posting of the keys did not violate the DMCA, and that it may be liable for misrepresentation.[8] Despite this, TI continued to send DMCA notices to websites that post the keys, but stopped doing so after late 2009. The EFF filed a DMCA Section 512 counter-notice on behalf of three of the bloggers who received DMCA notices. When the EFF did not receive a response by the deadline, the bloggers re-posted the content that had been taken down.[9]

See also[]

  • DeCSS
  • AACS encryption key controversy
  • Illegal number


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