20 years ago, some clever Microsoft engineers proposed a solution to this conundrum: "Trusted Computing." They proposed adding a second computer to your system, a sealed, secure chip with very little microcode, so little that it could all be audited in detail and purged of bugs.
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The chip itself would be securely affixed to your motherboard, such that any attempt to remove it and replace it with a compromised chip would be immediately obvious to you (for example, it might encapsulate some acid in a layer of epoxy that would rupture if you tried to remove the chip).
They called this "Next Generation Secure Computing Base," or "Palladium" for short. They came to the Electronic Frontier Foundation offices to present it. It was a memorable day:
https://pluralistic.net/2020/12/05/trusting-trust/#thompsons-devil
12/
The chip itself would be securely affixed to your motherboard, such that any attempt to remove it and replace it with a compromised chip would be immediately obvious to you (for example, it might encapsulate some acid in a layer of epoxy that would rupture if you tried to remove the chip).
They called this "Next Generation Secure Computing Base," or "Palladium" for short. They came to the Electronic Frontier Foundation offices to present it. It was a memorable day: