27 ms·

> The GPU still has no unique hardware private key, right? GPU's have had unique hardware private keys and secure memory for a decade.

_yb2s 2y ago
How does the remote streaming server know a key is an authentic hardware GPU that hasn't been compromised, and not something you just generated in software, to enable software level decryption of the media? It seems like you'd need some central SSL like certificate authority to verify and revoke credentials that were universally implemented in the same way by all GPU manufacturers.... surely there is no such thing?
- kbolino 2y ago
  At least for HDCP, that's exactly how it works. From the HDCP 2.2 spec [1]: > Device Key Set. An HDCP Receiver has a Device Key Set, which consists of its corresponding Device Secret Keys along with the associated Public Key Certificate. > Public Key Certificate. Each HDCP Receiver is issued a Public Key Certificate signed by DCP LLC, and contains the Receiver ID and RSA public key corresponding to the HDCP Receiver. > The top-level HDCP Transmitter checks to see if the Receiver ID of the connected device is found in the revocation list. [1]: https://www.digital-cp.com/sites/default/files/specifications/HDCP%20Interface%20Independent%20Adaptation%20Specification%20Rev2_2_FINAL.pdf https://www.digital-cp.com/sites/default/files/specification...
  - _yb2s 2y ago
    Thanks, that clarifies my confusion about how this could be realistically implemented. I couldn't see a practical way to verify every device on every connection via a central authority without massive scaling and reliability issues, but maintaining a small revocation list that can be cached everywhere media is distributed from seems quite practical.
    - mike_hearn 2y ago
      FWIW, efficient revocation has been solved since the Bluray era using AACS subset difference trees.
- mjg59 2y ago
  There doesn't need to be a central CA, you just need to establish trust with the DRM vendor. The GPU vendors coordinate with Microsoft to make Playready work, Android devices have certs that can be validated by Google for Widevine, Apple just does their own thing.

_yb2s 2y ago

How does the remote streaming server know a key is an authentic hardware GPU that hasn't been compromised, and not something you just generated in software, to enable software level decryption of the media? It seems like you'd need some central SSL like certificate authority to verify and revoke credentials that were universally implemented in the same way by all GPU manufacturers.... surely there is no such thing?

kbolino 2y ago
At least for HDCP, that's exactly how it works. From the HDCP 2.2 spec [1]: > Device Key Set. An HDCP Receiver has a Device Key Set, which consists of its corresponding Device Secret Keys along with the associated Public Key Certificate. > Public Key Certificate. Each HDCP Receiver is issued a Public Key Certificate signed by DCP LLC, and contains the Receiver ID and RSA public key corresponding to the HDCP Receiver. > The top-level HDCP Transmitter checks to see if the Receiver ID of the connected device is found in the revocation list. [1]: https://www.digital-cp.com/sites/default/files/specifications/HDCP%20Interface%20Independent%20Adaptation%20Specification%20Rev2_2_FINAL.pdf https://www.digital-cp.com/sites/default/files/specification...
- _yb2s 2y ago
  Thanks, that clarifies my confusion about how this could be realistically implemented. I couldn't see a practical way to verify every device on every connection via a central authority without massive scaling and reliability issues, but maintaining a small revocation list that can be cached everywhere media is distributed from seems quite practical.
  - mike_hearn 2y ago
    FWIW, efficient revocation has been solved since the Bluray era using AACS subset difference trees.
mjg59 2y ago
There doesn't need to be a central CA, you just need to establish trust with the DRM vendor. The GPU vendors coordinate with Microsoft to make Playready work, Android devices have certs that can be validated by Google for Widevine, Apple just does their own thing.