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Hacker News Hacker NewsI would love to see more focus on device manufacturers protecting the user instead of trying to protect themselves.
Prime example where the TPM could be fantastic: embedded devices that are centrally coordinated. For example, networking equipment. Imagine if all UniFi devices performed a measured boot and attested to their PCR values before the controller would provision them. This could give a very strong degree of security, even on untrusted networks and even if devices have been previously connected and provisioned by someone else. (Yes, there’s a window when you connect a device where someone else can provision it first.
But instead companies seem to obsess about protecting their IP even when there is almost no commercial harm to them when someone inevitably recovers the decrypted firmware image.
https://arxiv.org/abs/2304.14717
What a TPM does is provides a chip with some root key material (seeds) which can be extended with external data (PCRs) in a way which is a black box, and then that black box data can be used to perform cryptographic operations. So essentially, it is useful only for sealing data using the PCR state or attesting that the state matches.
This becomes an issue once you realize what's sending the PCR values; firmware which needs its own root of trust.
This takes you to Intel Boot Guard and AMD PSB/PSP, which implement traditional secure boot root of trust starting from a public key hash fused into the platform SoC. Without these systems, there's not really much point using a TPM, because an attacker could simply send the "correct" hashes for each PCR and reproduce the internal black-box TPM state for a "good" system.
Nothing prevents all the parties (the one you are attesting to and the central authority you use for indirection) to save everything and cross reference at any point in the future.
The same problem and often worse is present in DRM systems.
In the case of Widevine DRM you are actually leaking a static HWID to every license server, no collusion required. This is because there is no indirection involved, you give the license server the public key of the private key fused in the secure enclave for this purpose. The only safeguard is that every license server needs a certificate from Google to function (secure enclave will reject forming a request on invalid cert).
There are a lot of license servers.
As a side note, this is how they impose a cost on pirates. They employ forensic watermarks for the content streamed to subscribers - at the CDN level, they can do it cheaply using A/B watermarking, the cost is to store double the size of every file. When that content shows up in p2p piracy they trace it to the account and the device's DRM system public key and revoke its ability to view content (on the level of the license server) and ban the account.
ARM may have the market now… but RISC-V is the fastest growing and it may be poising to eat ARM’s lunch