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POST /api/v1/crypto/decrypt

Decrypt data.

Decrypts ciphertext under the key named by ttag.

ttag is REQUIRED here, unlike on encrypt. There is no minting arm: without a ttag the binding throws synchronously, before any request exists, which would reach the caller as a 500 rather than as the bad request it is -- so it is refused at the door.

A ciphertext that does not decrypt under the key ttag names -- encrypted under another key, damaged, or cut short -- is 422 DECRYPT_FAILED, not a denial: you were allowed to use the key, and these bytes are not what it produced. The ciphers are CBC modes (the default is AES-256-CBC), which carry no integrity check of their own, so a wrong key or a damaged ciphertext is detected only through the padding: about one time in 256 it is not, and the answer is 200 with bytes that are not your plaintext. Verify what you decrypt where that matters (an HMAC through POST /api/v1/crypto/hmac, say).

Authentication​

Send the session id as Authorization: Bearer <session id>, and an RFC 9449 DPoP proof in the DPoP header if your session is bound to a key. The two are required together, not as alternatives — see Authenticating and Proving you hold your key.

This surface sets no cookie

There is no session cookie on any response and none is read on any request. Do not set credentials: "include" on a browser fetch.

Request​

FieldTypeRequiredDescription
ciphertextstringyesCanonical base64.
ttagstringyesCanonical base64. Required.
ivstringnoCanonical base64. Optional.

Example

{
  "ciphertext": "...",
  "ttag": "...",
  "iv": "..."
}

Responses​

200​

Decrypted.

FieldTypeRequiredDescription
datastringyesbase64 of the plaintext. Treat as sensitive.
plaintextBytesintegeryes
ivSuppliedbooleanno

Example

{
  "data": "...",
  "plaintextBytes": 0,
  "ivSupplied": true
}

400​

The request was refused before anything was sent to the key server.

Most 400s on this surface carry code: BAD_REQUEST and a detail naming the field and saying what the key server would otherwise have done with it. A large share of them exist because the value would have been ACCEPTED downstream and quietly meant something else -- an empty string that reaches the wire as "mint a new key", a zero-length identifier that names no object, a numeric flag word that clears bits the caller did not name.

INVALID_ARGUMENT is the one 400 that DID reach the key server: the key server itself refused the argument (ERR_INVALID_ARGUMENT), and detail is its own sentence. On POST /api/v1/certificates/enroll that is a certificate that cannot authenticate -- certificate not permitted for authentication: keyUsage is present without digitalSignature (...), ... extendedKeyUsage is present without clientAuth (...), or certificate expired at enrolment: notAfter <UTC> ... -- and a multi-certificate body that carries one such leaf persists nothing.

KEY_UNWRAP_FAILED reached the key server too, on POST /api/v1/keys/import with format WRAPPED: the wrapped key did not unwrap under the key server's trust certificate -- wrapped to another key, by another method, or damaged. Nothing was stored for that key.

401​

No live session, a DPoP proof that did not verify, or a certificate session whose certificate the key server now refuses.

SESSION_NOT_FOUND -- the credential names no session this Gateway holds. SESSION_EXPIRED -- it aged out. Both carry reauth: true; obtain a new credential rather than retrying.

PROOF_* -- the sender constraint refused. See the DPoP section of this document for the full table; PROOF_MALFORMED is a 400 and PROOF_REPLAY_CACHE_FULL a 503, and the rest are here.

SCOPED_CREDENTIAL_EXPIRED -- a scoped browser credential passed its fixed lifetime. Use does not extend it: an idle timeout would be refreshed by exactly the traffic a stolen handle produces.

CERTIFICATE_REVOKED -- on a session established by certificate login, the key server re-checks the certificate that session was established with on its operations, and it is now named by revocation evidence. detail is the key server's sentence. The Gateway answers this once and then ENDS everything that service holds or minted here -- its sessions, the delegated sessions and the scoped credentials it minted -- so a later operation on any of them is SESSION_NOT_FOUND. Log in with a different certificate.

SSO_SESSION_EXPIRED -- a single-sign-on session (POST /api/v1/session/oidc) reached its lifetime, or was idle past its binding's idle bound; it has been ended. Sign in again.

SENDER_KEY_RETIRED -- the session's registered sender key was rotated out and its overlap has passed (see "The registered service's credential lifecycle"); the session is closed with this answer. SERVICE_REGISTRATION_ENDED -- the registration a service credential was issued under was removed or narrowed on this Gateway; it has ended. Both are final for that credential.

403​

ACL_DENIED (the key's access control list refuses you), ACCESS_DENIED (no role grants Decrypt Data), or OBJECT_NOT_IN_CREDENTIAL_SCOPE. A ciphertext that does not decrypt is 422, never 403.

410​

KEY_EXPIRED (retryable: false) -- the key the request named was expired (POST /api/v1/keys/expire). Its record is kept, and every use of it -- decrypt, encrypt under its t-Tag, export, an access-control grant or update -- is refused, on every key server of the deployment. An expiry is never undone; the key's owner may still remove it.

422​

DECRYPT_FAILED (retryable: false) -- the ciphertext does not decrypt under the key the request named: it was encrypted under another key, or it was damaged or cut short. You were authorized to use the key; the bytes are not what it produced, and sending them again fails the same way. detail is the key server's sentence. The key server records the refusal with the audit reason decryptFailed.

500​

A fault rather than a refusal.

OP_FAILED is the catch-all: the key server refused in words that match no classified pattern, so the Gateway cannot say more than that the operation did not happen. Some key server refusals that are conceptually a caller error arrive here rather than as a 4xx, because the wire carries no distinguishing code -- where a route can recognise one from its message it maps it, and each such mapping is documented on the operation.

503​

A capacity ceiling or a missing deployment prerequisite. retryable says which.

A scope of session or process names the ceiling that was hit, and the response carries Retry-After.

BUILD_NOT_ADMITTED (scope: process, retryable: true, Retry-After): the key server does not admit this Gateway's client build. Every key-server connection the Gateway opens attests the signed release it runs (TE_RELEASE_MANIFEST) right after it authenticates; while that attestation is refused -- the release is not registered at the key server's code-signing level, the level was raised under it, or the installed files no longer match the signed manifest -- every route but GET /api/v1/health and GET /api/v1/ready answers this, and detail names the cause. It is never a 401 or a 403: no credential or role of the caller's is at fault. The Gateway re-attempts on a timer and recovers without a restart once the key server admits it; GET /api/v1/ready says when.

CAPACITY_UNAVAILABLE (scope: process, retryable: true, Retry-After): this Gateway is serving its maximum number of requests at once, or cannot track another allowance, or (on a certificate login) is recording its maximum of live certificate sessions -- in which case the session the login created has been closed. Nothing else was sent to the key server. See "Rate and capacity limits" above.

413​

PAYLOAD_TOO_LARGE (retryable: false) -- the request body is larger than this deployment accepts. It was refused before it was parsed, and the connection is closed. Nothing was sent to the key server.

429​

RATE_LIMITED (retryable: true, Retry-After) -- the allowance this request is charged to is spent: the login allowance of its network source (before authentication), or the allowance, the concurrency ceiling or the live-session ceiling of the identity it was verified as -- shared by every session that identity holds, including every delegated and scoped credential a service minted. It carries no scope. Nothing was sent to the key server; on a login refused after authentication, the session it created has been closed. See "Rate and capacity limits" above.

Error handling​

Every failure answers JSON carrying at least code and detail. Match on code — detail is written for a human debugging the call and its wording is not part of the contract. See the error model.

StatusMeaning
400The request was refused before anything was sent to the key server. Most 400s on this surface carry code: BAD_REQUEST and a detail naming the field and saying what the key server would otherwise have done with it. A large share of them exist because the value would have been ACCEPTED downstream and quietly meant something else -- an empty string that reaches the wire as "mint a new key", a zero-length identifier that names no object, a numeric flag word that clears bits the caller did not name. INVALID_ARGUMENT is the one 400 that DID reach the key server: the key server itself refused the argument (ERR_INVALID_ARGUMENT), and detail is its own sentence. On POST /api/v1/certificates/enroll that is a certificate that cannot authenticate -- certificate not permitted for authentication: keyUsage is present without digitalSignature (...), ... extendedKeyUsage is present without clientAuth (...), or certificate expired at enrolment: notAfter <UTC> ... -- and a multi-certificate body that carries one such leaf persists nothing. KEY_UNWRAP_FAILED reached the key server too, on POST /api/v1/keys/import with format WRAPPED: the wrapped key did not unwrap under the key server's trust certificate -- wrapped to another key, by another method, or damaged. Nothing was stored for that key.
401No live session, a DPoP proof that did not verify, or a certificate session whose certificate the key server now refuses. SESSION_NOT_FOUND -- the credential names no session this Gateway holds. SESSION_EXPIRED -- it aged out. Both carry reauth: true; obtain a new credential rather than retrying. PROOF_* -- the sender constraint refused. See the DPoP section of this document for the full table; PROOF_MALFORMED is a 400 and PROOF_REPLAY_CACHE_FULL a 503, and the rest are here. SCOPED_CREDENTIAL_EXPIRED -- a scoped browser credential passed its fixed lifetime. Use does not extend it: an idle timeout would be refreshed by exactly the traffic a stolen handle produces. CERTIFICATE_REVOKED -- on a session established by certificate login, the key server re-checks the certificate that session was established with on its operations, and it is now named by revocation evidence. detail is the key server's sentence. The Gateway answers this once and then ENDS everything that service holds or minted here -- its sessions, the delegated sessions and the scoped credentials it minted -- so a later operation on any of them is SESSION_NOT_FOUND. Log in with a different certificate. SSO_SESSION_EXPIRED -- a single-sign-on session (POST /api/v1/session/oidc) reached its lifetime, or was idle past its binding's idle bound; it has been ended. Sign in again. SENDER_KEY_RETIRED -- the session's registered sender key was rotated out and its overlap has passed (see "The registered service's credential lifecycle"); the session is closed with this answer. SERVICE_REGISTRATION_ENDED -- the registration a service credential was issued under was removed or narrowed on this Gateway; it has ended. Both are final for that credential.
403ACL_DENIED (the key's access control list refuses you), ACCESS_DENIED (no role grants Decrypt Data), or OBJECT_NOT_IN_CREDENTIAL_SCOPE. A ciphertext that does not decrypt is 422, never 403.
410KEY_EXPIRED (retryable: false) -- the key the request named was expired (POST /api/v1/keys/expire). Its record is kept, and every use of it -- decrypt, encrypt under its t-Tag, export, an access-control grant or update -- is refused, on every key server of the deployment. An expiry is never undone; the key's owner may still remove it.
422DECRYPT_FAILED (retryable: false) -- the ciphertext does not decrypt under the key the request named: it was encrypted under another key, or it was damaged or cut short. You were authorized to use the key; the bytes are not what it produced, and sending them again fails the same way. detail is the key server's sentence. The key server records the refusal with the audit reason decryptFailed.
500A fault rather than a refusal. OP_FAILED is the catch-all: the key server refused in words that match no classified pattern, so the Gateway cannot say more than that the operation did not happen. Some key server refusals that are conceptually a caller error arrive here rather than as a 4xx, because the wire carries no distinguishing code -- where a route can recognise one from its message it maps it, and each such mapping is documented on the operation.
503A capacity ceiling or a missing deployment prerequisite. retryable says which. A scope of session or process names the ceiling that was hit, and the response carries Retry-After. BUILD_NOT_ADMITTED (scope: process, retryable: true, Retry-After): the key server does not admit this Gateway's client build. Every key-server connection the Gateway opens attests the signed release it runs (TE_RELEASE_MANIFEST) right after it authenticates; while that attestation is refused -- the release is not registered at the key server's code-signing level, the level was raised under it, or the installed files no longer match the signed manifest -- every route but GET /api/v1/health and GET /api/v1/ready answers this, and detail names the cause. It is never a 401 or a 403: no credential or role of the caller's is at fault. The Gateway re-attempts on a timer and recovers without a restart once the key server admits it; GET /api/v1/ready says when. CAPACITY_UNAVAILABLE (scope: process, retryable: true, Retry-After): this Gateway is serving its maximum number of requests at once, or cannot track another allowance, or (on a certificate login) is recording its maximum of live certificate sessions -- in which case the session the login created has been closed. Nothing else was sent to the key server. See "Rate and capacity limits" above.
413PAYLOAD_TOO_LARGE (retryable: false) -- the request body is larger than this deployment accepts. It was refused before it was parsed, and the connection is closed. Nothing was sent to the key server.
429RATE_LIMITED (retryable: true, Retry-After) -- the allowance this request is charged to is spent: the login allowance of its network source (before authentication), or the allowance, the concurrency ceiling or the live-session ceiling of the identity it was verified as -- shared by every session that identity holds, including every delegated and scoped credential a service minted. It carries no scope. Nothing was sent to the key server; on a login refused after authentication, the session it created has been closed. See "Rate and capacity limits" above.