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by bob10293 hours ago |
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upvoteby flippingheck2 hours ago|
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TPM is just a spec, it isn't necessarily a black box.

ARM TrustZone, for example, can run this OSS TPM: https://github.com/OP-TEE/optee_ftpm

I expect there are equivalents for Intel/AMD.

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upvoteby mjg593 hours ago|
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A dedicated HSM will give you stronger trust that the private key material can't be extracted, but there's no real way to bind an HSM to a specific client and that's a very easy thing to do in the vTPM case.
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upvoteby bob10292 hours ago|
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How often do we need to bind a specific machine to a specific key in the case of TLS?

In every case of TLS I've seen we are concerned with organizational identity, not machine identity. This effectively extends to client certificates in cases like B2B & vendor integration.

In both scenarios you would definitely want to use an HSM style solution.

Protecting the HSM from inappropriate use (proving you are allowed to sign using the keys within) is a problem orthogonal to protecting the key material. In cloud HSM applications, you often combine the cloud vendors managed identity solution and HSM policies to effectively bind a set of machines to a set of keys.

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upvoteby jon-wood1 hours ago|
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Any time you've got hardware and want to attest that it hasn't been tampered with before allowing it to interact with something like an API endpoint.

At work we deploy industrial IoT gateways, these are very much not end-user devices. We are actually concerned about the device's identity, and more specifically about being able to attest that the device is in fact the one we thought it was and it hasn't been tampered with. By putting the key for TLS client certificate in the device's TPM, locked behind attestation that what's been booted is what we expected to boot, we can have a reasonable degree of confidence that we're communicating with the device we thought we were rather than just someone who managed to copy the private key off disk.

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upvoteby mjg592 hours ago|
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In the given case - you want to bind communication to a given confidential compute instance, which means you want to be able to ensure that the communication is coming from within the confidential compute instance, which means you want to be able to prove that the private key is only accessible from within that instance. An HSM buys you nothing more there.
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