Signatures and MetafileChecksum
Have we seen this link ?
Basically it covers the MetafileChecksum and the signatures. Problem is I need an A, B, C of how to do the activities. I sort of guess that the public key is the same or failing that it can be read from the unit ?. Have we got that key yet ?.
The n in the example is a chunk of the public key.
I can't work out the process for doing "signature s raised to the power of 3 modulus n" (my two maths degrees were too long ago for that). I guess somewhere on the net there are some boxes to fill in that gives you the
I've loaded up openssl but I really need to know in simple terms using an online process or tool how to compute the process "signature s raised to the power of 3 modulus n".
Any help most appreciated. Having emulated the process described in the link, one then wants to see what it means for the MIB2.
I reckon if one mastered this then one can start editing the map upload files and anything else that needed signed files etc.
Edit you do the maths in python, I was kindly given the formulae for the worked example:
>>> x = pow(s, e, n)
Pick off this bit as per the worked example.
For the final bit to give the ANS.1 hex string which is the lock to the file. The metachecksum is locked to the rest of the file less the signature and the statement itself. The chipping away process and this program to get the SHA.1
The keys in the original post are applicable to the MIB2 High ones since I got the SLA.1 hash from the method to tally with the signatures that were protecting a VW POI upload file and a map update file. Haven't progressed it further yet, but interesting to note the public signatures are out there.
Perhaps all this is known....