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PICList Thread
'[PIC]: Encrypting Bootloader'
2002\03\19@025343 by Jeethu Rao

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I was just wondering if anyone has done anything like a bootloader
for PICs which takes Encrypted data and Decrypts it on the fly before
writing it to the PICs Program Memory ?

Jeethu Rao

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2002\03\19@041457 by uter van ooijen & floortje hanneman

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> I was just wondering if anyone has done anything like a bootloader
> for PICs which takes Encrypted data and Decrypts it on the fly before
> writing it to the PICs Program Memory ?

That's a one-banana trick, but what's the use when the code is there to read
for a programmer?
BTW does the 16f877a solve this problem?

Wouter van Ooijen
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2002\03\19@065704 by Jon Baker

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> I was just wondering if anyone has done anything like a bootloader
> for PICs which takes Encrypted data and Decrypts it on the fly before
> writing it to the PICs Program Memory ?

That would be quite a useful bit of software, unfortunately code protect
must be switched off for the areas you want to perform internal writes
on, so even if the external source for the program was encrypted, once the
PIC was flashed, the decrypted program could be read back using a normal
programmer.

The only way I can see to use achieve a similar goal, given that you really
need
a bootloader is to use an interpreted language, the PIC is programmed with
the
interpreter and is codeprotected, and decrypts and interprets the code on
the
fly as your program is executed.

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Jon Baker

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2002\03\19@162646 by Tony Nixon

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wouter van ooijen & floortje hanneman wrote:
>
> > I was just wondering if anyone has done anything like a bootloader
> > for PICs which takes Encrypted data and Decrypts it on the fly before
> > writing it to the PICs Program Memory ?
>
> That's a one-banana trick, but what's the use when the code is there to read
> for a programmer?
> BTW does the 16f877a solve this problem?

It appears that the normal code protection feature is retained, ie you
can't R/W through serial programming, but it also has added WRT bits to
disable Program Memory writes. I think this means that internally you
can read any ROM address regardless of code protection, but you cannot
modify ROM in any write protected areas.

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Best regards

Tony

mICros
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2002\03\19@164017 by Tony Nixon

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It looks like Bootloaders will need modifications for the new 16F87xA
series also, as the program memory write/read procedures have changed.

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Tony

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2002\03\20@074345 by Jeethu Rao

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Have these things been released yet ? Or will we have to wait ?
As of now they ain't available here in India.

Jeethu Rao


> {Original Message removed}

2002\03\20@151303 by uter van ooijen & floortje hanneman

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> It looks like Bootloaders will need modifications for the new 16F87xA
> series also, as the program memory write/read procedures have changed.

Correct, I had already implemented half of the changes when I checked
DigiKey and found that they have 0 in stock. Let's see when the 877a gets
available... BTW downloading should be a lot faster with the 877a.

Wouter van Ooijen
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Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen

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