[A83] Re: DS Thread Extended onto this list
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[A83] Re: DS Thread Extended onto this list
> At 03:28 PM 12/11/2002 -0800, you wrote:
> >(Lurk mode off :)
> >
> >>(See, to emulate the restriction, you'd have to know how to check for
> >>it, thus how to break it . . . )
> >
> >Not necesarrily. Actually checing to see if the os image is valid is
> >probably pretty easy. I assume the TI-83 does it in software, which
> means
> >both that VTI already checks the images (by vitrue of emulating the
> >calculator), and also anyone clever as disassembly could figure out how
> it
> >works. It's actually signing an OS image that's a bitch.
> >
> >I assume (though I'm not sure) that the signing system is a variation of
> >very well known and understood public-key encryption. TI signes their OS
>
> >with a secret, private-key. The OS can then be verified using a
> >public-key that can be stored in the TI-83 ROM. Because of some very
> >complicated math having to do with number theory, the public key can be
> >calculated using the private key, but not the other way around. This is
> >the way most digital content is securely signed these days.
> >
> >Thus, even though you can check to see if data is correctly signed, you
> >have no way of actually creating signed data yourself (without years of
> >CPU time spend brute-forcing the crypto).
>
> VTI doesn't emulate the os check. Just see by changing a string in a ROM
> image. I wonder, though. What if you load a hacked os in VTI, then use
> the Send Product Code feature of said OS to transmit to a real calc via
> the
> virtual link?
Did you mean the SendSW (<OS1.14?) or the SendOS (>=OS1.14) option? Don't
bother, I tried it.
--
Groeten,
Ronald Teune @School
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