Rahul Mehta wrote:
Pro-EVM folks are rejoicing and they cant even notice that things have blown on their faces.
In fact this disclosure improves the security by an order of magnitude!! Read my post above.
The code was burned into chip by Hitachi, not by BEL technicians. . And chip was made by Hitachi and so they can do every minor changes that are technologically possible and undetectable post-facto. So it it is factory programmed ROM for all practical purposes, different from OTP ROM where in equipment maker puts the code in his premises.
It is MASK ROM, which could be easily read by decapping. Also, any additional circuitry to the rest of the chip could be found by decapping as well.
So if a mole in BEL (top 3-4 guys) give out the source code to someone, that someone can add the modulo-5 logic to the code and get a new binary. And then Hitachi can put the tempered binary in chip instead of real one. And to hide it for good, Hitachi has to change the "GetHashCode" function in the chip so that it gives the hashcode of untempered code instead of hashcode of the tempered code sitting in the ROM.
BEL production verifies the image on the received chips. Also, at any time in the coming years, someone can do a forensic evaluation on the chips by decapping, and find it all out.
So my theory that you can temper 100000 EVMs with 10-12 people by putting module-5 logic in EVM code got better. You need co-operation from only top 3 guys in BEL. You dont need co-operation of any software coder, any QE guy, any QI guy etc of BEL. You do need co-operation of Hitachi CEO , but given the financial trouble Hitachi is facing, a phone call from Sonia with promise of buying $100 million worth of Hitachi share will convince him. And if that is not enough, another phone call from senior USG official will suffice. Hitachi wont risk losing US business for stupid 100,000 EVM chips' integrity.So any changes which cant be post-facto detected will be welcome.
All can be done, but everything blown out of the sky by a simple forensic analysis on the chip anytime in the coming decades.
So attn All pro-EVM folks,
1. Say you got a chip from Hitachi with some code in its ROM and lockbits set
2. Pls give exact steps you will follow to ensure that code in ROM is not tempered code, but promised code.
The lockbits are NOT set from the factory, but that notwithstanding,
You need EXACT steps? Try this:
1. Use a small grinder to remove bulk of the chip package
2. Use nitric acid, sodium hydroxide and acetone to expose the chip
3. Take magnified photographs of the chip. I would use the facility at my workplace.
4. Mark 1's and 0's on the photograph, and form them into bytes.
5. Copy the bytes into an ordered array.
6. Type it into the computer and convert into binary
You got the binary file.
If you see a discrepancy, you can go back to that particular bit on the photos and check. If you have doubt, you can use further magnification to take a decision.
There is no tech to read code of the ROM. Perhaps microscopic examination will reveal that it has few more gates. But even X-ray analysis wont tell you whether a bit at given address in ROM is 0 or 1. So you cant read the ROM. Now you are dependent on hashcode that processor gave you. So if Hitachi has modified the chip to give hashcode of promised code, then getting hashcode is useless and waste of time.
A simple microscope can do it. In fact I got an 800X microscope at home. It has very small FOV, but in a crunch, even that can be used!
I will write more after self-certified experts tell me how to verify ROM contents (and throw more insults, sarcasms, comments on incompetence and other assorted nonsenses they have been throwing in past 30 pages).
Oh, I am not self certified. I made my living dealing with bare silicon and GaAs chips and their packaging for a few years in last decade. Right now I make my living by design and programming of microcontroller based systems. I sit above a plant that produces thousands of products using bare silicon and GaAs chips in a day.
I would claim that you deserve every insult, merit every sarcasm, and every comment about your incompetence is glaringly true.
And I guarantee to dish more of them out as and when you shows a need of it.