<p>Generates a hash-based message authentication code (HMAC) for a message using an HMAC KMS key and a MAC algorithm that the key supports. HMAC KMS keys and the HMAC algorithms that KMS uses conform to industry standards defined in <a href="https://datatracker.ietf.org/doc/html/rfc2104">RFC 2104</a>.</p> <p>You can use value that GenerateMac returns in the <a>VerifyMac</a> operation to demonstrate that the original message has not changed. Also, because a secret key is used to create the hash, you can verify that the party that generated the hash has the required secret key. You can also use the raw result to implement HMAC-based algorithms such as key derivation functions. This operation is part of KMS support for HMAC KMS keys. For details, see <a href="https://docs.aws.amazon.com/kms/latest/developerguide/hmac.html">HMAC keys in KMS</a> in the <i> <i>Key Management Service Developer Guide</i> </i>.</p> <note> <p>Best practices recommend that you limit the time during which any signing mechanism, including an HMAC, is effective. This deters an attack where the actor uses a signed message to establish validity repeatedly or long after the message is superseded. HMAC tags do not include a timestamp, but you can include a timestamp in the token or message to help you detect when its time to refresh the HMAC. </p> </note> <p>The KMS key that you use for this operation must be in a compatible key state. For details, see <a href="https://docs.aws.amazon.com/kms/latest/developerguide/key-state.html">Key states of KMS keys</a> in the <i>Key Management Service Developer Guide</i>.</p> <p> <b>Cross-account use</b>: Yes. To perform this operation with a KMS key in a different Amazon Web Services account, specify the key ARN or alias ARN in the value of the <code>KeyId</code> parameter. </p> <p> <b>Required permissions</b>: <a href="https://docs.aws.amazon.com/kms/latest/developerguide/kms-api-permissions-reference.html">kms:GenerateMac</a> (key policy)</p> <p> <b>Related operations</b>: <a>VerifyMac</a> </p>

{
  "success": true,
  "data": {
    "id": "abc123",
    "created_at": "2025-01-01T00:00:00Z"
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters"
  }
}