REST Native Crypto API (/v1/crypto)¶

The Eviden KMS exposes a lightweight REST Native Crypto API under the /v1/crypto path. This API follows the JOSE (JSON Object Signing and Encryption) conventions from RFC 7516 (JWE), RFC 7515 (JWS), and RFC 7518 (JWA).

Key material never leaves the KMS. Only ciphertext, signatures, and MACs travel over the network.

Table of Contents¶

• Authentication
• Endpoints
  • POST /v1/crypto/keys
  • DELETE /v1/crypto/keys/{kid}
  • POST /v1/crypto/encrypt
  • POST /v1/crypto/decrypt
  • POST /v1/crypto/sign
  • POST /v1/crypto/verify
  • POST /v1/crypto/mac
• Error responses
• Known limitations
• Algorithm support matrix

Authentication¶

The /v1/crypto endpoints share the same authentication as the rest of the KMS API. Pass a JWT bearer token, a TLS client certificate, or an API token, depending on your server configuration. See Authentication.

Endpoints¶

POST /v1/crypto/keys¶

Generate a new cryptographic key (or key pair) in the KMS. The request follows JWK conventions — specify kty (key type) and alg (algorithm) at minimum.

Request body¶

{
  "kty": "oct",
  "alg": "A256GCM"
}

Response body¶

{
  "kid": "<key-uuid>",
  "kid_public": "<public-key-uuid>"  // only for asymmetric key pairs
}

Examples¶

Symmetric key (AES-256-GCM):

{ "kty": "oct", "alg": "A256GCM" }

RSA key pair (PS256):

{ "kty": "RSA", "alg": "PS256" }

EC key pair (ES256):

{ "kty": "EC", "crv": "P-256", "alg": "ES256" }

DELETE /v1/crypto/keys/{kid}¶

Destroy (permanently delete) a key from the KMS. The key is first revoked (deactivated) then removed from the database, including any linked public/private key in the pair.

Path parameters¶

Response¶

• 204 No Content on success (empty body).

POST /v1/crypto/encrypt¶

Encrypt plaintext using either:

• Direct encryption (alg=dir): uses a symmetric key directly as the content encryption key (CEK).
• RSA-OAEP key wrapping (alg=RSA-OAEP or alg=RSA-OAEP-256): generates an ephemeral CEK, wraps it with the RSA public key, and encrypts data with AES-GCM.

Supported alg values: dir, RSA-OAEP, RSA-OAEP-256. Supported enc values: A128GCM, A192GCM, A256GCM.

Flow — Direct (dir)¶

sequenceDiagram
    participant Client
    participant KMS
    Client->>KMS: POST /v1/crypto/keys {"kty":"oct","alg":"A256GCM"}
    KMS-->>Client: {"kid":""}
    Client->>KMS: POST /v1/crypto/encrypt {"kid":"","alg":"dir","enc":"A256GCM","data":"..."}
    Note over KMS: AES-GCM encrypt with symmetric key
    KMS-->>Client: {"protected":"...","encrypted_key":"","iv":"...","ciphertext":"...","tag":"..."}
    Client->>KMS: POST /v1/crypto/decrypt {"protected":"...","iv":"...","ciphertext":"...","tag":"..."}
    Note over KMS: AES-GCM decrypt with symmetric key
    KMS-->>Client: {"kid":"","data":"..."}
    Client->>KMS: DELETE /v1/crypto/keys/
    KMS-->>Client: 204 No Content

Flow — RSA-OAEP¶

sequenceDiagram
    participant Client
    participant KMS
    Client->>KMS: POST /v1/crypto/keys {"kty":"RSA","bits":2048}
    KMS-->>Client: {"kid":"","kid_public":""}
    Client->>KMS: POST /v1/crypto/encrypt {"kid":"","alg":"RSA-OAEP-256","enc":"A256GCM","data":"..."}
    Note over KMS: Generate ephemeral CEK
Wrap CEK with RSA-OAEP-256
AES-GCM encrypt data
Wipe CEK from memory
    KMS-->>Client: {"protected":"...","encrypted_key":"","iv":"...","ciphertext":"...","tag":"..."}
    Client->>KMS: POST /v1/crypto/decrypt {"protected":"...","encrypted_key":"","iv":"...","ciphertext":"...","tag":"..."}
    Note over KMS: RSA-OAEP unwrap → CEK
AES-GCM decrypt
(implicit rejection on OAEP failure)
    KMS-->>Client: {"kid":"","data":"..."}
    Client->>KMS: DELETE /v1/crypto/keys/
    KMS-->>Client: 204 No Content (cascades to public key)

Request body¶

{
  "kid": "<key-uuid>",
  "alg": "RSA-OAEP",
  "enc": "A256GCM",
  "data": "<base64url-encoded plaintext>",
  "aad": "<base64url-encoded AAD>"   // optional
}

Response body (Flattened JWE)¶

{
  "protected":     "<base64url JWE Protected Header>",
  "encrypted_key": "<base64url wrapped CEK>",
  "iv":            "<base64url IV>",
  "ciphertext":    "<base64url ciphertext>",
  "tag":           "<base64url GCM authentication tag>",
  "aad":           "<base64url AAD>"   // omitted when not supplied
}

For alg=dir, the encrypted_key field is an empty string. For RSA-OAEP, it contains the RSA-OAEP-wrapped CEK.

Example — Direct encryption (curl)¶

# 1. Create a 256-bit AES key
KID=$(curl -s -X POST https://kms.example.com/v1/crypto/keys \
  -H 'Content-Type: application/json' \
  -d '{"kty":"oct","alg":"A256GCM"}' | jq -r '.kid')

# 2. Encrypt
DATA_B64=$(printf 'Hello KMS!' | base64 | tr '+/' '-_' | tr -d '=')
JWE=$(curl -s -X POST https://kms.example.com/v1/crypto/encrypt \
  -H 'Content-Type: application/json' \
  -d "{\"kid\":\"$KID\",\"alg\":\"dir\",\"enc\":\"A256GCM\",\"data\":\"$DATA_B64\"}")

# 3. Decrypt
curl -s -X POST https://kms.example.com/v1/crypto/decrypt \
  -H 'Content-Type: application/json' \
  -d "$JWE" | jq -r '.data | @base64d'

# 4. Clean up
curl -s -X DELETE https://kms.example.com/v1/crypto/keys/$KID

Example — RSA-OAEP (curl)¶

# 1. Create an RSA-2048 key pair
KEYS=$(curl -s -X POST https://kms.example.com/v1/crypto/keys \
  -H 'Content-Type: application/json' \
  -d '{"kty":"RSA","bits":2048}')
KID=$(echo "$KEYS" | jq -r '.kid')
KID_PUB=$(echo "$KEYS" | jq -r '.kid_public')

# 2. Encrypt with RSA-OAEP-256 using the public key
DATA_B64=$(printf 'Secret message' | base64 | tr '+/' '-_' | tr -d '=')
JWE=$(curl -s -X POST https://kms.example.com/v1/crypto/encrypt \
  -H 'Content-Type: application/json' \
  -d "{\"kid\":\"$KID_PUB\",\"alg\":\"RSA-OAEP-256\",\"enc\":\"A256GCM\",\"data\":\"$DATA_B64\"}")

# 3. Decrypt (kid in protected header resolves to private key automatically)
curl -s -X POST https://kms.example.com/v1/crypto/decrypt \
  -H 'Content-Type: application/json' \
  -d "$JWE" | jq -r '.data | @base64d'

# 4. Clean up (cascades to the linked public key)
curl -s -X DELETE https://kms.example.com/v1/crypto/keys/$KID

POST /v1/crypto/decrypt¶

Decrypt a Flattened JWE token.

Supports both alg=dir (direct AES-GCM) and alg=RSA-OAEP/RSA-OAEP-256 (RSA-OAEP key unwrapping + AES-GCM content decryption).

The kid in the JWE protected header identifies the decryption key. For RSA-OAEP, this can be either the private key or the public key UUID (the server resolves to the private key automatically).

The decrypt endpoint has no standalone flow diagram — it is the second half of the encrypt/decrypt flows shown in the encrypt section above.

Request body¶

{
  "protected":     "<base64url JWE Protected Header>",
  "encrypted_key": "<base64url wrapped CEK>",
  "iv":            "<base64url IV>",
  "ciphertext":    "<base64url ciphertext>",
  "tag":           "<base64url GCM authentication tag>",
  "aad":           "<base64url AAD>"  // optional; must match the value used during encryption
}

Response body¶

{
  "kid":  "<key-uuid>",
  "data": "<base64url plaintext>"
}

Security: implicit rejection¶

For RSA-OAEP decryption, the server implements implicit rejection as recommended by RFC 7516 §11.5. If the RSA-OAEP unwrap fails (indicating a tampered or invalid encrypted_key), the server substitutes a random CEK and proceeds with AES-GCM decryption — which will fail with the same generic “Decryption failed” error. This prevents padding oracle attacks.

Example (curl)¶

# JWE is the JSON response from POST /v1/crypto/encrypt
PLAINTEXT=$(curl -s -X POST https://kms.example.com/v1/crypto/decrypt \
  -H 'Content-Type: application/json' \
  -d "$JWE" | jq -r '.data | @base64d')
echo "$PLAINTEXT"

POST /v1/crypto/sign¶

Sign data using an asymmetric private key. Returns a detached JWS (payload not included in the response).

Supported algorithms: RS256, RS384, RS512, PS256, PS384, PS512, ES256, ES384, ES512; EdDSA and MLDSA44 (non-FIPS builds only).

Flow — Sign and verify¶

sequenceDiagram
    participant Client
    participant KMS
    Client->>KMS: POST /v1/crypto/keys {"kty":"RSA","alg":"PS256"}
    KMS-->>Client: {"kid":"","kid_public":""}
    Client->>KMS: POST /v1/crypto/sign {"kid":"","alg":"PS256","data":""}
    Note over KMS: RSA-PSS sign with private key
    KMS-->>Client: {"protected":"","signature":""}
    Client->>KMS: POST /v1/crypto/verify {"protected":"","data":"","signature":""}
    Note over KMS: Decode protected header → kid
Fetch public key
RSA-PSS verify
    KMS-->>Client: {"kid":"","valid":true}
    Client->>KMS: DELETE /v1/crypto/keys/
    KMS-->>Client: 204 No Content (cascades to public key)

Request body¶

{
  "kid":  "<private-key-uuid>",
  "alg":  "RS256",
  "data": "<base64url payload>"
}

Response body¶

{
  "protected": "<base64url JWS Protected Header>",
  "signature": "<base64url signature>"
}

Example (curl)¶

# 1. Create an RSA-2048 key pair
KEYS=$(curl -s -X POST https://kms.example.com/v1/crypto/keys \
  -H 'Content-Type: application/json' \
  -d '{"kty":"RSA","alg":"RS256"}')
KID=$(echo "$KEYS" | jq -r '.kid')

# 2. Sign
DATA_B64=$(printf 'data to sign' | base64 | tr '+/' '-_' | tr -d '=')
SIGN_RESP=$(curl -s -X POST https://kms.example.com/v1/crypto/sign \
  -H 'Content-Type: application/json' \
  -d "{\"kid\":\"$KID\",\"alg\":\"RS256\",\"data\":\"$DATA_B64\"}")

# 3. Verify
curl -s -X POST https://kms.example.com/v1/crypto/verify \
  -H 'Content-Type: application/json' \
  -d "$(jq -n --argjson s "$SIGN_RESP" --arg d "$DATA_B64" \
       '{protected:$s.protected,data:$d,signature:$s.signature}')"

# 4. Clean up
curl -s -X DELETE https://kms.example.com/v1/crypto/keys/$KID

POST /v1/crypto/verify¶

Verify a detached JWS signature. The KMS looks up the public key from the protected header.

Required: the JWS protected header decoded from protected must contain a kid field set to the KMS public key UUID. Requests without kid are rejected with 400. This field is set automatically by POST /v1/crypto/sign.

The verify endpoint is the second half of the sign/verify flow shown in the sign section above.

Request body¶

{
  "protected": "<base64url JWS Protected Header (contains kid + alg)>",
  "data":      "<base64url payload>",
  "signature": "<base64url signature>"
}

Response body¶

{
  "kid":   "<public-key-uuid>",
  "valid": true   // false when the signature does not match
}

POST /v1/crypto/mac¶

Compute or verify a MAC (Message Authentication Code).

• Compute: omit the mac field → the KMS returns the computed MAC value.
• Verify: include the mac field → the KMS returns valid: true/false.

Supported algorithms: HS256, HS384, HS512.

Flow — MAC compute and verify¶

sequenceDiagram
    participant Client
    participant KMS
    Client->>KMS: POST /v1/crypto/keys {"kty":"oct","alg":"HS256"}
    KMS-->>Client: {"kid":""}
    Client->>KMS: POST /v1/crypto/mac {"kid":"","alg":"HS256","data":""}
    Note over KMS: HMAC-SHA256 compute
    KMS-->>Client: {"kid":"","mac":""}
    Client->>KMS: POST /v1/crypto/mac {"kid":"","alg":"HS256","data":"","mac":""}
    Note over KMS: HMAC-SHA256 verify
    KMS-->>Client: {"kid":"","valid":true}
    Client->>KMS: DELETE /v1/crypto/keys/
    KMS-->>Client: 204 No Content

Request body¶

{
  "kid":  "<key-uuid>",
  "alg":  "HS256",
  "data": "<base64url data>",
  "mac":  "<base64url MAC to verify>"  // omit to compute
}

Response body — compute¶

{
  "kid": "<key-uuid>",
  "mac": "<base64url MAC>"
}

Response body — verify¶

{
  "kid":   "<key-uuid>",
  "valid": true   // false when the MAC does not match
}

RFC 7515 §A.1 known-answer vector¶

The MAC value below is pinned by an integration test (test_rfc7515_a1_hs256_known_answer). It reproduces the exact HS256 result from RFC 7515 §Appendix A.1.

Example (curl)¶

# 1. Create an HMAC-SHA256 key
KID=$(curl -s -X POST https://kms.example.com/v1/crypto/keys \
  -H 'Content-Type: application/json' \
  -d '{"kty":"oct","alg":"HS256"}' | jq -r '.kid')

# 2. Compute MAC
DATA_B64=$(printf 'message' | base64 | tr '+/' '-_' | tr -d '=')
MAC_RESP=$(curl -s -X POST https://kms.example.com/v1/crypto/mac \
  -H 'Content-Type: application/json' \
  -d "{\"kid\":\"$KID\",\"alg\":\"HS256\",\"data\":\"$DATA_B64\"}")
MAC_VALUE=$(echo "$MAC_RESP" | jq -r '.mac')

# 3. Verify MAC
curl -s -X POST https://kms.example.com/v1/crypto/mac \
  -H 'Content-Type: application/json' \
  -d "{\"kid\":\"$KID\",\"alg\":\"HS256\",\"data\":\"$DATA_B64\",\"mac\":\"$MAC_VALUE\"}"

# 4. Clean up
curl -s -X DELETE https://kms.example.com/v1/crypto/keys/$KID

Error responses¶

All endpoints return a JSON body { "error": "<type>", "description": "<detail>" } with an appropriate HTTP status code:

Known limitations¶

The following JOSE features are not yet implemented in this API.

Full RFC 7515 §A.2/A.3/A.4 known-answer tests are deferred until kid-less verification is supported (current tests do round-trips with freshly generated keys).

Algorithm support matrix¶

Key management algorithms (alg)¶

Content encryption algorithms (enc)¶

Signature algorithms¶

MAC algorithms¶