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Comment: Re:I don't see why this is such a big deal (Score 1) 301

by Lionel Debroux (#36191160) Attached to: TI vs. Calculator Hobbyists, the Next Round

You're partially missing the point ;)
On the one hand, of course, TI is actively trying to block arbitrary native code execution on the platform - and failing at it.
But on the other hand, Lua programming is about using something that TI themselves (silently) put into the OS. And TI broke what we had been using so far, documents made of compressed+encrypted part copied from TI's own documents and a part merely compressed. We're back to a situation where only TI can _easily_ generate Lua documents that OS 3.0.2 understands... until the encryption of all document parts is documented and replicated by third parties...

Comment: Re:Best answer (Score 1) 417

by Lionel Debroux (#32943436) Attached to: TI vs. Calculator Hobbyists, Again

As written in the grandparent of your post, everything in the Nspire is signed. The first-stage boot1 is not rewritable; the second-stage boot is signed and checked by the boot1; the OS is signed and checked by the boot2.
Signature is done through 1024-bit RSA public keys, we can easily extract all of these keys... but it's not practical to factor them: three-four orders of magnitude more difficult than the state of the art (currently approximately 768 bits), which is itself three-four orders of magnitude more difficult than the 512-bit RSA keys of TI-Z80 and TI-68k calcs that we factored last year.

Therefore, we can't just "destroy the firmware check absolutely" off-line, we have to do it on-calc... and doing so requires exploiting the OS... and finding reliable exploits requires reverse-engineering, fuzzing, etc.

Comment: Re:What about TI's freedom? (Score 1) 417

by Lionel Debroux (#32942326) Attached to: TI vs. Calculator Hobbyists, Again

> If anything it's the Ndless community that's being counterproductive here.
I wouldn't call making calculators more useful to users (it's not just about games - see, on TI-68k calculators, lower-level access to the OS does enable us to do more powerful functionality and do it faster) "counterproductive" ;-)

Comment: Re:Best answer (Score 1) 417

by Lionel Debroux (#32942304) Attached to: TI vs. Calculator Hobbyists, Again

Exactly, mod parent up.
While we can (and do) build our own OS for TI-Z80 and TI-68k calculators, especially since we factored the RSA public keys used for signature (but before that on both series, in a more hack-ish way), TI has taken significant extra effort for preventing us from doing the same on Nspire calculators. Multiple layers of signature with 1024-bit RSA keys, to begin with.

And we're already working on reverse-engineering OS 2.1 ;)

Comment: Re:Standardized tests (Score 1) 417

by Lionel Debroux (#32942260) Attached to: TI vs. Calculator Hobbyists, Again

> amajor part of TI's calculator business is created by the un-hackability of their calculators.
On the contrary: it's a fact that their past calculator lines, TI-Z80 and TI-68k, are _very_ hackable. Yet they sold millions of them (and it's precisely their hackability - games - that makes them more desirable for users than a number of other calculator models) !

Comment: Re:How long since you were in school? (Score 1) 417

by Lionel Debroux (#32942248) Attached to: TI vs. Calculator Hobbyists, Again

People deciding the blunder of banning TI calculators from education would be _severely_ incompetent:
* an unfixable exploit which enables hack-ish installation of arbitrarily modified OS on TI-68k calculators has been known for 11 years... but it did not get TI calculators banned from standardized tests for that very reason.

* the factorization of all interesting 512-bit RSA public keys used for signature of OS and FlashApps, and therefore the seamless installation of arbitrarily modified OS (resigned with the deduced private keys) on TI-Z80 and TI-68k calculators, was made in 2009... but again, it did not get TI calculators banned from standardized tests for that very reason.
Nowadays, we're even fixing TI's bugs for them (there's an unofficial patch for the terribly unstable OS 2.53 MP for 84+ - the bugfix was reported months ago to TI, but they still don't provide it to users).

Comment: Re:Whats wrong with the world? (Score 1) 417

by Lionel Debroux (#32942236) Attached to: TI vs. Calculator Hobbyists, Again

I'm not really convinced that too much functionality would hurt sales - but it's a fact that the lackluster functionality of Nspire calculators, prior to Ndless, _did_ hurt sales ;-)
It's pretty easy to understand why: Nspires are expensive, and users don't get much for their money. The first version of the OS didn't even contain any form of BASIC programming (!!), and that four years later, the BASIC of Nspires remains sub-par compared to the TI-Z80 and TI-68k BASIC.

As for TI calculators being banned from education... people deciding such a blunder would be _severely_ incompetent:
* an unfixable exploit which enables hack-ish installation of arbitrarily modified OS on TI-68k calculators has been known for 11 years... but it did not get TI calculators banned from standardized tests for that very reason.

* the factorization of all interesting 512-bit RSA public keys used for signature of OS and FlashApps, and therefore the seamless installation of arbitrarily modified OS (resigned with the deduced private keys) on TI-Z80 and TI-68k calculators, was made in 2009... but again, it did not get TI calculators banned from standardized tests for that very reason.
Nowadays, we're even fixing TI's bugs for them (there's an unofficial patch for the terribly unstable OS 2.53 MP for 84+).

Hardware Hacking

TI vs. Calculator Hobbyists, Again 417

Posted by timothy
from the p0wning-the-market's-not-enough dept.
Deep Thought writes "Texas Instruments, already infamous thanks to the signing key controversy last year, is trying a new trick to lock down its graphing calculators, this time directed toward its newest TI-Nspire line. The TI-Nspires were already the most controlled of TI's various calculator models, and no third-party development of any kind (except for its very limited form of TI-BASIC) was allowed until the release of the independent tool Ndless. Since its release, TI has been determined to prevent the large calculator programming community from using it. Its latest released operating system for the Nspire family (version 2.1) now prevents the calculators from downgrading to OS 1.1, needed to run Ndless. This is TI's second major attack on Ndless, as the company has already demanded that websites posting the required OS 1.1 remove it from public download [PDF, in French], obviously to prevent use of the tool. Once again, TI is preventing calculator hobbyists from running their own software on calculators they bought and paid for."

Every young man should have a hobby: learning how to handle money is the best one. -- Jack Hurley

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