Pranav wrote:It is also pertinent to mention 3D stacked IC's - so examination of the surface of a chip does not necessarily tell you all about the circuitry.
Dileep, Tanaji, Raja Bose and Company claims that every bit can be read no matter what ROM is used. Lets believe them for the time being.
Btw, if chip can be read that only means that some EVMs still have trojan code. This does NOT stop them from putting rigged code, as the chip gets examined by a very few people, if at all they do bit level examination. For all I know, they might be doing just functional tests. So even if chip can be read back, that is only a speed breaker and not show stopper.
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To show the ludicrity of the claim that the BEL CEO can do mischief directly, let us look at the organizational structure of a huge company like BEL.
BEL is majority owned by GOI, and the CEO is the CMD, appointed by GOI. BEL has 9 factories, and employ 12000+ people. The corporate office is in Nagavara, Bangalore. The EVMS are designed at the R&D facility in Bangalore, and manufactured at the Navi Mumbai and/or Bangalore facilities.
Each location have its head, reporting to the board of directors (not to the CEO). The bangalore complex in Jalahall have a director for the whole operation, and the other manufacturing operations have GMs. The R&D will be under one GM, reporting to the director, and under him, there will be a group manager for the commercial products.
The EVM group will be under a manager in that group. He will have managers for the hardware and software teams. The software team will have one leader.
It is practically impossible to byepass any of the hierarchy. In fact, the CEO can not even go to the R&D facility without a formal visit plan, along with his entourage, and joined by the GM and everyone in the chain.
..... Whether it is BEL, or Hitachi, the CEO is virtually powerless to influence the technical side of the business.
Dileep,
Pls spell PwC for me.
So to break this process, I need to buy out
1. BEL CEO
2. Director of Hyderabad of banglore facility who makes EVM
3. EVM unit head
Three senior guys ONLY. No need to buy directors - they wont get a clue.
And in middle/junior guys, I need to buy out the team lead of coding (if I want to put trojan using random encryption) or guy in HW in charge of testing chips (if Hitachi is putting a different code).
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Dileep,
If Encryption is simple, decryption will not take too much space on chip. eg consider encryption of byte as
8 actual bits = 4 actual bits + 4 random bits + 4 random bytes + 4 actual next bits .
Basically, insert 32 random bits between half-bytes (nibble?). So if code is 1K bytes, the encrypted version will take 1/2 + 1/2 + + 4 + 1/2 + 1/2 = 5k bytes.
So decryption is : read 40 bits and take first 4 and last 4 bits, and ignore the 32 bits in between. The decrypted code is not stored. Microcode can decrypt 2-3 bytes at a time, the result comes into code register where it is executed.
Now microcode implements 50-100 instructions . So few more instruction will increase number of gates by a small %. Even if it is detectable. But then, you are assuming that BEL was actually verifying the entire chip layout, gate by gate when the chip came. And if yes, the team lead of HW verification can put a rigged code in the PC used for verification which when gets tempered design will report the right design.