[thu2111]

You can't use the ecosystem of services if you use SEV. Think about it: if your encrypted web server VM stores data in a Google-provided SQL database, your data is no longer encrypted. Or if you're using Google-provided SSL termination, or Google provided key hosting, or Google managed operating systems, or Google-provided AI, or Google-provided log analytics.

If you need to protect your data, all of those services are no longer usable.

[theevilsharpie]

None of these things are incompatible with a VM running SEV. In fact, since many of Google's managed services themselves use Compute Engine, they may already support Confidential VM's running SEV.

[thu2111]

It's irrelevant. You can't audit those services because they're Google-proprietary software, and you aren't the ones with administrator access to them.

This stuff is new, so I think there's going to be a lot of confusion about what it means and how it works. But the basic concept is easy. SEV and SGX don't mean anything except that you can remotely audit a piece of software that's running by checking the hash of the code that was loaded, and that code can derive private encryption keys unavailable (in theory) to any other piece of software on the system, and that its memory is encrypted.

In SEV that piece of code is effectively the entire OS. In SGX it's a much smaller piece of code, more like a single shared library.

With a Google managed database system, you don't know what software it precisely is. These clouds aren't open source. Even the hypervisors aren't open source, as far as I know. Even when based on an open source product there are proprietary patches. And, they change constantly.

That means if your VM starts up and you get a hash back saying it's the OS you wanted to start, that's great, but the moment you open a connection to some other server even if it's all running on AMD hardware, all you get back is a hash and moreover (iirc with SEV) a random hash that's only useful if you're actually the one that started the remote VM. With SGX you get the actual code hash and/or code signing key, even if you didn't start it, which is a bit better.

What does that hash actually mean? Unless you can reproduce the build of whatever you're talking to and audit the code to look for back doors, and keep auditing it as it changes, it means basically nothing. That's why SGX focuses on really tiny pieces of code - less attack surface, but also less audit churn and easier reproducibility.

Ultimately to have guarantees your data is private in a cloud, you need either to audit the software stacks and rely on hardware roots of trust, or you can use clever forms of encryption like FHE. But just ticking a check box by itself does nothing at all.

[theevilsharpie]

> This stuff is new, so I think there's going to be a lot of confusion about what it means and how it works.

SEV is a hardware function that provides real-time memory encryption. That's all. Maintaining full confidentiality beyond the boundaries of the processor's memory controller is not within the scope of SEV.

Google Cloud's Confidential Computing platform _may_ offer a broader solution with some type of cryptographic guarantee, using SEV as a component of the solution. I don't know how far they are, or if that's the direction that they're looking to take the platform.

However, if you're looking for a platform with remote attestation that the computing environment is fully trusted, SEV is not sufficient. You would need a traditional TEE for that.

> just ticking a check box by itself does nothing at all.

Taken directly from Google's blog post:

"Confidential VMs can help all our customers protect sensitive data, but we think it will be _especially interesting to those in regulated industries._"

(Emphasis mine)

It provides additional hardware-backed protection when sharing a physical machine with other tenants, which among other things, can make shared hosting a possibility for security-conscious environments that previously prohibited it.

If that doesn't sound like a useful feature, or you feel that it's theater, then you're probably not the target market for the feature.

[thu2111]

SEV is a hardware function that provides real-time memory encryption. That's all.

You're demonstrating my point for me. That isn't all, by any means. SEV is primarily implemented in firmware, and provides a form of measured boot and remote attestation. Don't take my word for it:

https://developer.amd.com/sev/

"AMD Secure Processor. Provides cryptographic functionality for secure key generation and key management."

This is literally the second feature of two that it advertises as part of SEV.

Those parts are critical and SEV doesn't really mean anything without it. RAM encryption is only useful if you don't trust the owner of the host hardware. But if you don't trust the host, you can't assume they switched on RAM encryption or booted the OS you asked for into the VM, you have to check it. That's what the remote attestation lets you do.

If that doesn't sound like a useful feature, or you feel that it's theater, then you're probably not the target market for the feature.

I work in regulated markets! And yes, it's true, there's a lot of regulators that can be satisfied with security theatre. The weakness of regulator understanding of technology isn't, by itself, a reason to consider SEV without RA useful.