---
title: "POST /#X-Amz-Target=TrentService.VerifyMac"
method: POST
path: "/#X-Amz-Target=TrentService.VerifyMac"
---

# POST /#X-Amz-Target=TrentService.VerifyMac

`POST /#X-Amz-Target=TrentService.VerifyMac`

Verifies the hash-based message authentication code (HMAC) for a specified message, HMAC KMS key, and MAC algorithm. To verify the HMAC, `VerifyMac` computes an HMAC using the message, HMAC KMS key, and MAC algorithm that you specify, and compares the computed HMAC to the HMAC that you specify. If the HMACs are identical, the verification succeeds; otherwise, it fails. Verification indicates that the message hasn't changed since the HMAC was calculated, and the specified key was used to generate and verify the HMAC.

HMAC KMS keys and the HMAC algorithms that KMS uses conform to industry standards defined in [RFC 2104](https://datatracker.ietf.org/doc/html/rfc2104).

This operation is part of KMS support for HMAC KMS keys. For details, see [HMAC keys in KMS](https://docs.aws.amazon.com/kms/latest/developerguide/hmac.html) in the _Key Management Service Developer Guide_.

The KMS key that you use for this operation must be in a compatible key state. For details, see [Key states of KMS keys](https://docs.aws.amazon.com/kms/latest/developerguide/key-state.html) in the _Key Management Service Developer Guide_.

**Cross-account use**: 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 `KeyId` parameter.

**Required permissions**: [kms:VerifyMac](https://docs.aws.amazon.com/kms/latest/developerguide/kms-api-permissions-reference.html) (key policy)

**Related operations**: GenerateMac

## Headers

- `X-Amz-Target` 'TrentService.VerifyMac', required

## Request body

- VerifyMacRequest
  - `Message` string, password, required — <p>The message that will be used in the verification. Enter the same message that was used to generate the HMAC.</p> <p> <a>GenerateMac</a> and <code>VerifyMac</code> do not provide special handling for message digests. If you generated an HMAC for a hash digest of a message, you must verify the HMAC for the same hash digest.</p>
  - `KeyId` string, required — <p>The KMS key that will be used in the verification.</p> <p>Enter a key ID of the KMS key that was used to generate the HMAC. If you identify a different KMS key, the <code>VerifyMac</code> operation fails.</p>
  - `MacAlgorithm` 'HMAC_SHA_224' | 'HMAC_SHA_256' | 'HMAC_SHA_384' | 'HMAC_SHA_512', required — The MAC algorithm that will be used in the verification. Enter the same MAC algorithm that was used to compute the HMAC. This algorithm must be supported by the HMAC KMS key identified by the <code>KeyId</code> parameter.
  - `Mac` string, required — The HMAC to verify. Enter the HMAC that was generated by the <a>GenerateMac</a> operation when you specified the same message, HMAC KMS key, and MAC algorithm as the values specified in this request.
  - `GrantTokens` GrantTokenType[] — <p>A list of grant tokens.</p> <p>Use a grant token when your permission to call this operation comes from a new grant that has not yet achieved <i>eventual consistency</i>. For more information, see <a href="https://docs.aws.amazon.com/kms/latest/developerguide/grants.html#grant_token">Grant token</a> and <a href="https://docs.aws.amazon.com/kms/latest/developerguide/grant-manage.html#using-grant-token">Using a grant token</a> in the <i>Key Management Service Developer Guide</i>.</p>

## Response `200`

Success

- VerifyMacResponse
  - `KeyId` string — The HMAC KMS key used in the verification.
  - `MacValid` boolean — <p>A Boolean value that indicates whether the HMAC was verified. A value of <code>True</code> indicates that the HMAC (<code>Mac</code>) was generated with the specified <code>Message</code>, HMAC KMS key (<code>KeyID</code>) and <code>MacAlgorithm.</code>.</p> <p>If the HMAC is not verified, the <code>VerifyMac</code> operation fails with a <code>KMSInvalidMacException</code> exception. This exception indicates that one or more of the inputs changed since the HMAC was computed.</p>
  - `MacAlgorithm` 'HMAC_SHA_224' | 'HMAC_SHA_256' | 'HMAC_SHA_384' | 'HMAC_SHA_512' — The MAC algorithm used in the verification.

## Other responses

- `480` — NotFoundException
- `481` — DisabledException
- `482` — KeyUnavailableException
- `483` — InvalidKeyUsageException
- `484` — InvalidGrantTokenException
- `485` — KMSInternalException
- `486` — KMSInvalidMacException
- `487` — KMSInvalidStateException

---

[API](https://skmtc.net/aws/apis/kms.md) · [All operations](https://skmtc.net/aws/apis/kms/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/aws/kms/versions/f92d678d2025/schema)