Lesson 1.1 · 12 min read
Data in use: the missing third state
Encryption at rest and in transit are routine. Confidential computing targets the moment data is decrypted to be processed.
Three states of data
Security programs have long protected data at rest (disk and object encryption) and in transit (TLS, IPsec, VPNs). Both are mature and widely mandated. But to compute on data, a program has to decrypt it into memory. At that point the plaintext is visible to anything with enough privilege on the host: the operating system kernel, the hypervisor, firmware, a host administrator, a debugger, or someone with physical access to the memory bus.
The Confidential Computing Consortium (CCC), a Linux Foundation project, defines confidential computing as the protection of data in use by performing computation in a hardware-based, attested Trusted Execution Environment. Each part of that definition matters to an officer:
- Hardware-based: the isolation is enforced by the CPU (or GPU), not by a software policy that a privileged administrator could change.
- Attested: the environment can produce cryptographic evidence of what it is running, so a remote party can decide whether to trust it before releasing data or keys.
- Trusted Execution Environment (TEE): a region of execution whose memory is protected for confidentiality and integrity against software outside it.
| State | Typical control | Who can still read plaintext? |
|---|---|---|
| At rest | Disk, database, or object-store encryption with KMS-managed keys | Any process that holds or can request the key once the data is loaded |
| In transit | TLS 1.3, mTLS, IPsec | Both endpoints, and anything that terminates TLS (load balancers, proxies) |
| In use | Confidential computing (TEE + attestation) | Only code inside the attested TEE; the host OS, hypervisor, and operators are outside the boundary |
Why organizations adopt it
The common drivers are: processing regulated or highly sensitive data on shared cloud infrastructure; protecting proprietary AI model weights and customer prompts; multi-party collaboration where no single party should see the others' raw data; and reducing the set of insiders who could access plaintext. In each case the core question is the same: who must we be able to exclude, and can we prove we excluded them?
Key takeaways
- Confidential computing protects data in use; at-rest and in-transit controls remain required.
- The CCC definition has three parts: hardware-based, attested, TEE. A product missing attestation is not confidential computing in the CCC sense.
- Start every engagement by asking which privileged parties the design must exclude.