Key control (BYOK and HYOK)
In shortEncryption with provider-held keys protects against thieves, not against authorities.
"All data is encrypted" appears on every vendor page. The statement is true and answers the wrong question. What matters is not whether encryption happens, but who holds the key.
The three models
Provider-managed keys. The default. The provider encrypts and decrypts because it owns the key. That protects against stolen disks and against staff without authorisation. It does not protect against a lawful order served on the provider, because the provider is technically able to comply.
BYOK — bring your own key. You generate the key and import it into the provider's key management system. You can withdraw it, which ends access. While it is imported, however, the provider can use it. BYOK improves auditability; it does not change who has control.
HYOK — hold your own key. The key never leaves your environment. The provider only ever sees ciphertext and cannot resolve it, no matter who asks. This is the only variant that genuinely takes the provider out of the equation.
Why this matters legally
In its recommendations following Schrems II, the European Data Protection Board stated explicitly: encryption is an effective supplementary measure only where the third-country provider does not hold the key and cannot obtain it. See Schrems II.
That turns a technical choice into a legal one.
The price
HYOK is inconvenient. Server-side search, thumbnails, full-text indexes and most analytics stop working when the service cannot read the content. That is not a defect; it is the point.
So the usual route is not all-or-nothing but a split: HYOK for the small body of data where an access order would really hurt, provider-managed keys for the rest.