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by snuxoll 3292 days ago
SGX is an interesting technology from a security perspective, but the use of it for DRM going forward really worries me, I'm tired of not owning my content and hoping companies don't go out of business and money I've spent goes up in smoke.
1 comments
ngneer 3292 days ago
Agreed. Thus far it appears that Intel itself has been vacillating with regard to launch enclave policy. As a reminder, all technology can be used for good or evil, whatever your definitions of those may be. The issue is one of control, but you can defer worrying about DRM until trusted I/O gets implemented.
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snuxoll 3292 days ago
SGX already works with the PVAP doesn't it? I can't imagine Netflix would be using SGX-based DRM for 4K content unless it actually provided a real benefit, especially considering without trusted I/O it's much more obvious where to grab decrypted data by looking for SGX-related instructions.
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future1979 3291 days ago
I looked into sgx recently and have a question related to your comment. It seems an enclave doesn't make system calls. I was wondering how any io gets done? You mention untrusted ... is that the only way??? Trust zone seems to do it better then?
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ngneer 3288 days ago
An enclave does not make any system calls directly like the rest of the process would, but a system call can definitely be made through the use of a shim layer. In SGX parlance, calls to the outside of the enclave are known as OCALLs. The danger with relying on values returned by a syscall is that the OS could be lying. As an exercise, you could implement a simple "hello, world" filesystem driver that hides the presence of certain files. So, as long as the enclave has no trusted path to I/O, it must rely on the operating system, which is assumed compromised. If the enclave decrypts protected content for the sake of having those be written to the display by the OS, then you can see that the contents are not secure. SGX support for PAVP means that the chipset is involved in shuttling the data into and out of the enclave, with no one being able to interject. Not sure TrustZone solves this.

Just came across this interesting article: https://arxiv.org/pdf/1701.01061

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