[E3-hacking] Just got an e3 - where do I start
edd.robbins at googlemail.com
Wed Oct 17 13:58:59 BST 2012
> Cliff Lawson, the creator of the Emailer family, might know who owns the
> rights and how to go about contacting them. I'll send you his email
> address off-list. If they are effectively bricks without the Amstrad
> infrastructure support then he may like to see them getting some use by
> being opened up more.
Some progress - I recently finished some work so had some free time to
look at the emailer again. I emailed Cliff Lawson (thanks for the
contact Ralph) and he does indeed seem willing to help. He gave me
some information about how the images are signed in PBL 5.1! He says:
"all I can tell you is that the signature I added uses SHA256 and the
key is the first two or three sentences of the King James Bible ("In
the beginning was the word...").
note that SHA256 like all hashses (MD5 etc) is sensitive to every last
space and bit of punctuation so even if you get the words right if you
miss a comma or a semi-colon it will not sign. Again I forget the
exact details but I did it very like CHAP authentication so first the
"key" and then the bytes of the image are passed through the hash and
then I cannot remember if the SHA256 hash output was then put in the
header or a footer to the image and the PBL also has the key built in
(actually I think it may be held like a module in Nand) it passes that
then the delivered data through an SHA256 and only if it gets the same
hash does it unlock the flash programming routines."
So not quite there, but this might be enough to reverse engineer the
format enough to get PBL5.1 machines to accept an image. If I
understand correctly with PBL5.1 the machine wont accept an image over
serial though, so this would have to be done by dialling in to another
Cliff did say he will have a look and see if he can find any source
code that might have more information. In which case we might not have
to go through the reverse engineering stage, but I'm not certain he
will actually find anything.
I actually went ahead and bought another new emailer as well - and it
was brand new, unopened. So it has PBL4.9 and my need to get the other
one working has kind of gone.
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