Re: A89: Linux Port for 89/92
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Re: A89: Linux Port for 89/92
I should also have put the word trivial in quotes, meaning it is trivial to
understand the process, not necessarily meaning something one could do
overnight.
-Adam
Johan wrote:
>
> Adam Davis wrote:
> >
> > It is a trivial matter to brute force break the code. We just need someone
> > willing to hook the calc to their computer.
>
> While the .tib file is being downloaded, the boot loader calculates a
> checksum of the code. At the end of the .tib file, there is an RSA encrypted
> version of the same checksum. The boot loader decrypts the checksum and
> verifies that the calculated one equals to the decrypted one and refuses to
> run the code if they don't match.
>
> The key that is required for *decrypting* is available to us, but we can't
> *encrypt* our own checksum.
>
> The RSA key that TI uses is 512 bits and the MD5 checksum is 128 bits.
> Trying to adapt a ROM to get a specific checksum is would take (on average)
> 10^25 years if the computer can do one million tests per second. Breaking
> the RSA would take 10^140 years for the same computer.
>
> If you still think it's a "trivial matter", please tell me and the rest of
> the list how you are going to deal with it!
>
> //Johan
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