[A83] Re: apps

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[A83] Re: apps


> To my knowledge, it tells the calc to allow apps that are signed with
> the developer signature.
...Applications are signed with a key for a specific ID.  For example, the
shareware/freeware key (which is available only to TI) signs applications
for the 0104 ID (my personal ID is 9F04).  All calculators can load
applications signed for the 0104 ID.  When you sign an application with a
key, it creates some sort of data (I'll call it a checksum) which is used by
the calculator to validate the application.
When you load the application onto the calculator, it's checked against the
certificates you have loaded onto your calculator, and if you don't have the
required certificate, the calculator rejects the application.

> But hey, if someone were to make his developer certificate and signing
> available to anyone,
> we could simply sign apps with that signature, and put the specific
> developer signature with it.
...This would not work.  The problem is with the developer certificate.
Certificates are also validated when sent to the calculator.  This time,
it's validated based on your serial number.  Of course, there's encryption
involved, so you can't just open up the certificate file and change the
numbers.  So if you have the same serial number as someone else (which
obviously you don't), you could load their certificates, and thus their
applications.  Otherwise, you're stuck.

> But, since we know TI longer than today, they 'll probably have included
> some statement in some license, stating it to be "illegal" to distribute
> one's developer certificate and signings...
...As far as I know, there is no such clause in any license.  Just having a
key and certificate doesn't help you at all.  Just like if someone purchases
an application from TI, they can send the application to you and you wont be
able to use it.

-Dan Englender

----- Original Message -----
> To my knowledge, it tells the calc to allow apps that are signed with
> the developer signature.
>
> But hey, if someone were to make his developer certificate and signing
> available to anyone,
> we could simply sign apps with that signature, and put the specific
> developer signature with it.
>
> But, since we know TI longer than today, they 'll probably have included
> some statement in some license, stating it to be "illegal" to distribute
> one's developer certificate and signings...
>
> Someone, please verify this!!
>
> ...and think of some legal trick to circumvent this. (e.g. making all
> apps made with that certificate "beta stage" (officially, that is) in
> case they stated that the dev certif. can only be used for beta testing
> apps...)
>
> --Peter Martijn
>
> Gavin Olson wrote:
>
> >> You send them the unsigned application, and they sign it.  You can make
> >> applications yourself, and run them on your calc if you get a developer
> >> certificate for your calc from TI.  Or use their Flash Simulator, or
the
> >> upcoming VTI.  I wrote a plugin for Assembly Studio 8x to make
applications
> >> (.hex files).
> >
> >
> > What does this developer certificate on the calc do to make unsigned
apps
> > work?
> >
> >
> >
> >
> >
>
>
>
>
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