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TI-83 Plus OS Signing Key Cracked
Posted by Michael on 31 July 2009, 15:33 GMT

The ever-mysterious Benjamin Moody posted a cryptic message on the United-TI forum yesterday. In it, he listed the factorization of the 512-bit RSA modulus used by TI's OS signing key for the 83+ (the "0004 key"). No other details are yet available about how he achieved this feat of substantial brute forcing power. In the event of United-TI downtime, Brandon Wilson has put a copy of Benjamin's values on his personal website.

With this achievement, any operating system can be cryptographically signed in a manner identical to that of the original TI-OS. Third party operating systems can thus be loaded on any 83+ calculators without the use of any extra software (that was mentioned in recent news) Complete programming freedom has finally been achieved on the TI-83 Plus!

Update: Benjamin has posted additional details on the United-TI forum thread.

Update: A distributed computing project has been set up. Information about how to join the effort to crack the OS keys for the remaining TI models can be found here.

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Re: TI-83 Plus OS Signing Key Cracked
graphmastur Account Info

Hey, I thought you left TI as news editor.

Anyway, yes, this is very monumental. It would have taken him forever. I still want to know how he did it.

Reply to this comment    31 July 2009, 15:43 GMT


Re: Re: TI-83 Plus OS Signing Key Cracked
Michael Vincent  Account Info
(Web Page)

I thought I did too :) I'll still be around now and then.

I'm very impressed by Benjamin's work. I just wish we could get some technical details!

Reply to this comment    31 July 2009, 16:16 GMT


Re: Re: Re: TI-83 Plus OS Signing Key Cracked
graphmastur Account Info

I know, he's being so secretive about it.

I just wish that someone writes a tutorial on how to fully make an os, or that brandon writes one documenting what he did with os2. If not, and if I ever figure out all of this, I will probably write one!!!

Reply to this comment    31 July 2009, 16:23 GMT


Re: Re: Re: Re: TI-83 Plus OS Signing Key Cracked
Lewk Account Info
(Web Page)

Clearly he converted a TI-83+ into some sort of quantum computing device, enabling him to crack it.

Reply to this comment    31 July 2009, 19:37 GMT


Re: Re: Re: Re: Re: TI-83 Plus OS Signing Key Cracked
Benjamin Moody  Account Info

Hmm... good idea. Quantum Voyage 400, anyone? :)

Reply to this comment    31 July 2009, 19:49 GMT


Re: Re: Re: Re: Re: Re: TI-83 Plus OS Signing Key Cracked
Person Dude Account Info

I agree. The Voyage 400 is the next key to work on.

Reply to this comment    29 August 2009, 14:13 GMT


Re: Re: Re: Re: Re: Re: Re: TI-83 Plus OS Signing Key Cracked
Person Dude Account Info

Oh... I misread the previous comment, but still, the voyage 400 should be the next key to crack. Because of its advanced computing capacity and color screen, though, it may take a while.

Reply to this comment    30 August 2009, 01:38 GMT

Re: TI-83 Plus OS Signing Key Cracked
Benjamin Moody  Account Info

As I said on UTI, this took a fair amount of CPU power -- about 73 days of computation -- but it didn't really take a lot of work from me; mostly I just watched the numbers go up, and periodically started up another Msieve run.

Oh, and by the way, I don't actually think this will work for sending OSes to a stock 84+. (84+ OSes are signed using the 0A key instead. While the boot code does include key 04, it also has a bug preventing that key from being used. So I believe you can only send an 04-signed OS if you have that key in your calculator certificate.)

Reply to this comment    31 July 2009, 19:47 GMT

Re: Re: TI-83 Plus OS Signing Key Cracked
Jason Malinowski  Account Info
(Web Page)

Ah, so it was "brute force" (although smart brute forcing) rather than something else. I never thought about how weak 512-bit RSA keys are, but clearly you shouldn't use them. ;-) Too bad we didn't just do this a year or two ago by pooling a few CPUs together...

But in any case, brilliant work!

Reply to this comment    1 August 2009, 03:12 GMT


Re: Re: TI-83 Plus OS Signing Key Cracked
Ronakbhai Account Info

*sigh* This makes me wish I didn't fall of out of the programming loop. I just barely understand what all was done, but it's a far fetch for me to get up and have a go at it now...

Reply to this comment    5 August 2009, 18:06 GMT

Re: TI-83 Plus OS Signing Key Cracked
bfr Account Info
(Web Page)

Awesome! This, along with the news about what Brandon did, suddenly made me have an extreme urge to do some TI-83+ series assembly

Reply to this comment    1 August 2009, 00:45 GMT


Re: Re: TI-83 Plus OS Signing Key Cracked
Brandon Wilson  Account Info
(Web Page)

Good! That's the intention!

Reply to this comment    1 August 2009, 07:04 GMT

Re: TI-83 Plus OS Signing Key Cracked
haveacalc  Account Info

We need 4 million people willing to take part in distributed computing.

Reply to this comment    1 August 2009, 02:07 GMT


Re: Re: TI-83 Plus OS Signing Key Cracked
IAmACalculator Account Info

Actually, with just 73 computers equal to Ben's, the sieving could theroetically be done within a day.

Reply to this comment    1 August 2009, 15:24 GMT


Re: Re: Re: TI-83 Plus OS Signing Key Cracked
Benjamin Moody  Account Info

The sieving, maybe, but the final processing would still take a week or so.

Reply to this comment    2 August 2009, 01:52 GMT

Re: TI-83 Plus OS Signing Key Cracked
Tabarnaco Account Info

Okay.
And what about the 83+SE/84+/84+SE?

Reply to this comment    23 August 2009, 05:31 GMT


Re: Re: TI-83 Plus OS Signing Key Cracked
Benjamin Moody  Account Info
(Web Page)

Funny you should ask. The 83+ SE uses the same keys as the normal 83+. But the OS signing key for the 84+ has just been factored by a distributed effort (see the link.) We're still working to find the factors of the remaining keys (OS and app signing keys for TI-73, 89, 92+, and V200.) You can help, too; see http://boinc.unsads.com/rsals/ .

Reply to this comment    26 August 2009, 06:02 GMT

Re: TI-83 Plus OS Signing Key Cracked
Joe Young  Account Info

TI has used the DMCA to throw C&Ds at us :(

Reply to this comment    30 August 2009, 12:23 GMT

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