Confidential computing in the cloud
TEEs that protect data in use from the host itself: SGX enclaves, TDX and SEV-SNP confidential VMs, Arm CCA realms, attestation-gated key release in KMS, the side-channel record and when the cost is worth paying.
01Data in use and the TEE landscape
- Explain what a trusted execution environment protects and from whom
- Compare SGX enclaves with TDX, SEV-SNP and Arm CCA confidential VMs
- Design key release on attestation with cloud KMS policies
- Name the side-channel history and what it means for your threat model
- Decide when confidential computing is worth the cost and when it is theatre
Encryption at rest and in transit leave one gap: data is plaintext in memory while it is being processed, and the hypervisor, the host OS, a cloud admin or a cold-boot attacker can read that memory. Confidential computing closes the gap with a trusted execution environment (TEE): CPU-enforced isolation plus memory encryption, so that even privileged host software cannot read or silently modify the protected workload, and remote attestation so that you can prove it before trusting it with secrets.
| Technology | Isolation unit | Trusted computing base | Attestation root | Notes |
|---|---|---|---|---|
| Intel SGX | Enclave inside a process | CPU plus enclave code only | Intel (DCAP, ECDSA quotes) | Smallest TCB; app must be partitioned; removed from recent client CPUs, still on Xeon |
| Intel TDX | Whole VM (trust domain) | CPU, TDX module, guest OS | Intel quote with MRTD and RTMR registers | Lift and shift a VM; the hypervisor is outside the TCB |
| AMD SEV-SNP | Whole VM | AMD secure processor, guest OS | Report signed by a chip-unique VCEK chained to AMD's root | Adds integrity (reverse map table) to SEV memory encryption |
| Arm CCA | Realm VM | Realm management monitor, guest OS | Arm CCA token from the platform | Armv9 RME; cloud availability still early |
| AWS Nitro Enclaves | Carved-out VM with no network or storage | Nitro hypervisor and card | Nitro attestation document with PCRs | Not a CPU TEE; trusts AWS Nitro, not the parent instance |
The big shift since 2021 is from enclaves (rewrite your app into trusted and untrusted halves) to confidential VMs (run an unmodified OS in an encrypted VM). The TCB grows, because the whole guest kernel is now trusted, but adoption becomes realistic. Confidential containers (the CNCF CoCo project, AKS confidential containers) go one step further: each pod runs in its own lightweight confidential VM via Kata, so the Kubernetes node is outside the TCB.
Interviewers test whether you know who a TEE defends against. The answer is the host: hypervisor, host OS, cloud operator, other tenants. It does not defend the workload from its own bugs. An SQL injection in a confidential VM is still an SQL injection.
This is an advanced module
Hardware roots of trust & confidential computing is part of the Pro pass. 3 more sections — the deep dives, the final design, follow-ups and the test — unlock with it.
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