# Verify Verifies a digital signature that was generated by the [Sign](API_Sign.md) operation. Verification confirms that an authorized user signed the message with the specified KMS key and signing algorithm, and the message hasn't changed since it was signed. If the signature is verified, the value of the `SignatureValid` field in the response is `True`. If the signature verification fails, the `Verify` operation fails with an `KMSInvalidSignatureException` exception. A digital signature is generated by using the private key in an asymmetric KMS key. The signature is verified by using the public key in the same asymmetric KMS key. For information about asymmetric KMS keys, see [Asymmetric KMS keys](https://docs.aws.amazon.com/kms/latest/developerguide/symmetric-asymmetric.html) in the * AWS Key Management Service Developer Guide*. To use the `Verify` operation, specify the same asymmetric KMS key, message, and signing algorithm that were used to produce the signature. The message type does not need to be the same as the one used for signing, but it must indicate whether the value of the `Message` parameter should be hashed as part of the verification process. You can also verify the digital signature by using the public key of the KMS key outside of AWS KMS. Use the [GetPublicKey](API_GetPublicKey.md) operation to download the public key in the asymmetric KMS key and then use the public key to verify the signature outside of AWS KMS. The advantage of using the `Verify` operation is that it is performed within AWS KMS. As a result, it's easy to call, the operation is performed within the FIPS boundary, it is logged in AWS CloudTrail, and you can use key policy and IAM policy to determine who is authorized to use the KMS key to verify signatures. To verify a signature outside of AWS KMS with an SM2 public key (China Regions only), you must specify the distinguishing ID. By default, AWS KMS uses `1234567812345678` as the distinguishing ID. For more information, see [Offline verification with SM2 key pairs](https://docs.aws.amazon.com/kms/latest/developerguide/offline-operations.html#key-spec-sm-offline-verification). The KMS key that you use for this operation must be in a compatible key state. For details, see [Key states of AWS KMS keys](https://docs.aws.amazon.com/kms/latest/developerguide/key-state.html) in the * AWS Key Management Service Developer Guide*. **Cross-account use**: Yes. To perform this operation with a KMS key in a different AWS account, specify the key ARN or alias ARN in the value of the `KeyId` parameter. **Required permissions**: [kms:Verify](https://docs.aws.amazon.com/kms/latest/developerguide/kms-api-permissions-reference.html) (key policy) **Related operations**: [Sign](API_Sign.md) **Eventual consistency**: The AWS KMS API follows an eventual consistency model. For more information, see [AWS KMS eventual consistency](https://docs.aws.amazon.com/kms/latest/developerguide/accessing-kms.html#programming-eventual-consistency). ## Request Syntax ``` { "DryRun": boolean, "GrantTokens": [ "string" ], "KeyId": "string", "Message": blob, "MessageType": "string", "Signature": blob, "SigningAlgorithm": "string" } ``` ## Request Parameters For information about the parameters that are common to all actions, see [Common Parameters](CommonParameters.md). The request accepts the following data in JSON format. **Note** In the following list, the required parameters are described first. ** [KeyId](#API_Verify_RequestSyntax) ** Identifies the asymmetric KMS key that will be used to verify the signature. This must be the same KMS key that was used to generate the signature. If you specify a different KMS key, the signature verification fails. To specify a KMS key, use its key ID, key ARN, alias name, or alias ARN. When using an alias name, prefix it with `"alias/"`. To specify a KMS key in a different AWS account, you must use the key ARN or alias ARN. For example: + Key ID: `1234abcd-12ab-34cd-56ef-1234567890ab` + Key ARN: `arn:aws:kms:us-east-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab` + Alias name: `alias/ExampleAlias` + Alias ARN: `arn:aws:kms:us-east-2:111122223333:alias/ExampleAlias` To get the key ID and key ARN for a KMS key, use [ListKeys](API_ListKeys.md) or [DescribeKey](API_DescribeKey.md). To get the alias name and alias ARN, use [ListAliases](API_ListAliases.md). Type: String Length Constraints: Minimum length of 1. Maximum length of 2048. Required: Yes ** [Message](#API_Verify_RequestSyntax) ** Specifies the message that was signed. You can submit a raw message of up to 4096 bytes, or a hash digest of the message. If you submit a digest, use the `MessageType` parameter with a value of `DIGEST`. If the message specified here is different from the message that was signed, the signature verification fails. A message and its hash digest are considered to be the same message. Type: Base64-encoded binary data object Length Constraints: Minimum length of 1. Maximum length of 4096. Required: Yes ** [Signature](#API_Verify_RequestSyntax) ** The signature that the `Sign` operation generated. Type: Base64-encoded binary data object Length Constraints: Minimum length of 1. Maximum length of 6144. Required: Yes ** [SigningAlgorithm](#API_Verify_RequestSyntax) ** The signing algorithm that was used to sign the message. If you submit a different algorithm, the signature verification fails. Type: String Valid Values: `RSASSA_PSS_SHA_256 | RSASSA_PSS_SHA_384 | RSASSA_PSS_SHA_512 | RSASSA_PKCS1_V1_5_SHA_256 | RSASSA_PKCS1_V1_5_SHA_384 | RSASSA_PKCS1_V1_5_SHA_512 | ECDSA_SHA_256 | ECDSA_SHA_384 | ECDSA_SHA_512 | SM2DSA | ML_DSA_SHAKE_256 | ED25519_SHA_512 | ED25519_PH_SHA_512` Required: Yes ** [DryRun](#API_Verify_RequestSyntax) ** Checks if your request will succeed. `DryRun` is an optional parameter. To learn more about how to use this parameter, see [Testing your permissions](https://docs.aws.amazon.com/kms/latest/developerguide/testing-permissions.html) in the * AWS Key Management Service Developer Guide*. Type: Boolean Required: No ** [GrantTokens](#API_Verify_RequestSyntax) ** A list of grant tokens. Use a grant token when your permission to call this operation comes from a new grant that has not yet achieved *eventual consistency*. For more information, see [Grant token](https://docs.aws.amazon.com/kms/latest/developerguide/grants.html#grant_token) and [Using a grant token](https://docs.aws.amazon.com/kms/latest/developerguide/using-grant-token.html) in the * AWS Key Management Service Developer Guide*. Type: Array of strings Array Members: Minimum number of 0 items. Maximum number of 10 items. Length Constraints: Minimum length of 1. Maximum length of 8192. Required: No ** [MessageType](#API_Verify_RequestSyntax) ** Tells AWS KMS whether the value of the `Message` parameter should be hashed as part of the signing algorithm. Use `RAW` for unhashed messages; use `DIGEST` for message digests, which are already hashed; use `EXTERNAL_MU` for 64-byte representative μ used in ML-DSA signing as defined in NIST FIPS 204 Section 6.2. When the value of `MessageType` is `RAW`, AWS KMS uses the standard signing algorithm, which begins with a hash function. When the value is `DIGEST`, AWS KMS skips the hashing step in the signing algorithm. When the value is `EXTERNAL_MU` AWS KMS skips the concatenated hashing of the public key hash and the message done in the ML-DSA signing algorithm. Use the `DIGEST` or `EXTERNAL_MU` value only when the value of the `Message` parameter is a message digest. If you use the `DIGEST` value with an unhashed message, the security of the signing operation can be compromised. When using ECC\$1NIST\$1EDWARDS25519 KMS keys: + ED25519\$1SHA\$1512 signing algorithm requires AWS KMS `MessageType:RAW` + ED25519\$1PH\$1SHA\$1512 signing algorithm requires AWS KMS `MessageType:DIGEST` When you specify the ED25519\$1PH\$1SHA\$1512 signing algorithm with `MessageType:DIGEST`, AWS KMS still performs the SHA-512 prehash described in [Step 1 of Section 7.8.1 in FIPS 186-5](https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-5.pdf#page=39). This means the input is hashed twice: once by you and once by KMS. When the value of `MessageType` is `DIGEST`, the length of the `Message` value must match the length of hashed messages for the specified signing algorithm. When the value of `MessageType` is `EXTERNAL_MU` the length of the `Message` value must be 64 bytes. You can submit a message digest and omit the `MessageType` or specify `RAW` so the digest is hashed again while signing. However, if the signed message is hashed once while signing, but twice while verifying, verification fails, even when the message hasn't changed. The hashing algorithm that `Verify` uses is based on the `SigningAlgorithm` value. + Signing algorithms that end in SHA\$1256 use the SHA\$1256 hashing algorithm. + Signing algorithms that end in SHA\$1384 use the SHA\$1384 hashing algorithm. + Signing algorithms that end in SHA\$1512 use the SHA\$1512 hashing algorithm. + Signing algorithms that end in SHAKE\$1256 use the SHAKE\$1256 hashing algorithm. + SM2DSA uses the SM3 hashing algorithm. For details, see [Offline verification with SM2 key pairs](https://docs.aws.amazon.com/kms/latest/developerguide/offline-operations.html#key-spec-sm-offline-verification). Type: String Valid Values: `RAW | DIGEST | EXTERNAL_MU` Required: No ## Response Syntax ``` { "KeyId": "string", "SignatureValid": boolean, "SigningAlgorithm": "string" } ``` ## Response Elements If the action is successful, the service sends back an HTTP 200 response. The following data is returned in JSON format by the service. ** [KeyId](#API_Verify_ResponseSyntax) ** The Amazon Resource Name ([key ARN](https://docs.aws.amazon.com/kms/latest/developerguide/concepts.html#key-id-key-ARN)) of the asymmetric KMS key that was used to verify the signature. Type: String Length Constraints: Minimum length of 1. Maximum length of 2048. ** [SignatureValid](#API_Verify_ResponseSyntax) ** A Boolean value that indicates whether the signature was verified. A value of `True` indicates that the `Signature` was produced by signing the `Message` with the specified `KeyID` and `SigningAlgorithm.` If the signature is not verified, the `Verify` operation fails with a `KMSInvalidSignatureException` exception. Type: Boolean ** [SigningAlgorithm](#API_Verify_ResponseSyntax) ** The signing algorithm that was used to verify the signature. Type: String Valid Values: `RSASSA_PSS_SHA_256 | RSASSA_PSS_SHA_384 | RSASSA_PSS_SHA_512 | RSASSA_PKCS1_V1_5_SHA_256 | RSASSA_PKCS1_V1_5_SHA_384 | RSASSA_PKCS1_V1_5_SHA_512 | ECDSA_SHA_256 | ECDSA_SHA_384 | ECDSA_SHA_512 | SM2DSA | ML_DSA_SHAKE_256 | ED25519_SHA_512 | ED25519_PH_SHA_512` ## Errors For information about the errors that are common to all actions, see [Common Error Types](CommonErrors.md). ** DependencyTimeoutException ** The system timed out while trying to fulfill the request. You can retry the request. HTTP Status Code: 500 ** DisabledException ** The request was rejected because the specified KMS key is not enabled. HTTP Status Code: 400 ** DryRunOperationException ** The request was rejected because the DryRun parameter was specified. HTTP Status Code: 400 ** InvalidGrantTokenException ** The request was rejected because the specified grant token is not valid. HTTP Status Code: 400 ** InvalidKeyUsageException ** The request was rejected for one of the following reasons: + The `KeyUsage` value of the KMS key is incompatible with the API operation. + The encryption algorithm or signing algorithm specified for the operation is incompatible with the type of key material in the KMS key `(KeySpec`). For encrypting, decrypting, re-encrypting, and generating data keys, the `KeyUsage` must be `ENCRYPT_DECRYPT`. For signing and verifying messages, the `KeyUsage` must be `SIGN_VERIFY`. For generating and verifying message authentication codes (MACs), the `KeyUsage` must be `GENERATE_VERIFY_MAC`. For deriving key agreement secrets, the `KeyUsage` must be `KEY_AGREEMENT`. To find the `KeyUsage` of a KMS key, use the [DescribeKey](API_DescribeKey.md) operation. To find the encryption or signing algorithms supported for a particular KMS key, use the [DescribeKey](API_DescribeKey.md) operation. HTTP Status Code: 400 ** KeyUnavailableException ** The request was rejected because the specified KMS key was not available. You can retry the request. HTTP Status Code: 500 ** KMSInternalException ** The request was rejected because an internal exception occurred. The request can be retried. HTTP Status Code: 500 ** KMSInvalidSignatureException ** The request was rejected because the signature verification failed. Signature verification fails when it cannot confirm that signature was produced by signing the specified message with the specified KMS key and signing algorithm. HTTP Status Code: 400 ** KMSInvalidStateException ** The request was rejected because the state of the specified resource is not valid for this request. This exceptions means one of the following: + The key state of the KMS key is not compatible with the operation. To find the key state, use the [DescribeKey](API_DescribeKey.md) operation. For more information about which key states are compatible with each AWS KMS operation, see [Key states of AWS KMS keys](https://docs.aws.amazon.com/kms/latest/developerguide/key-state.html) in the * * AWS Key Management Service Developer Guide* *. + For cryptographic operations on KMS keys in custom key stores, this exception represents a general failure with many possible causes. To identify the cause, see the error message that accompanies the exception. HTTP Status Code: 400 ** NotFoundException ** The request was rejected because the specified entity or resource could not be found. HTTP Status Code: 400 ## See Also For more information about using this API in one of the language-specific AWS SDKs, see the following: + [AWS Command Line Interface V2](https://docs.aws.amazon.com/goto/cli2/kms-2014-11-01/Verify) + [AWS SDK for .NET V4](https://docs.aws.amazon.com/goto/DotNetSDKV4/kms-2014-11-01/Verify) + [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/kms-2014-11-01/Verify) + [AWS SDK for Go v2](https://docs.aws.amazon.com/goto/SdkForGoV2/kms-2014-11-01/Verify) + [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/kms-2014-11-01/Verify) + [AWS SDK for JavaScript V3](https://docs.aws.amazon.com/goto/SdkForJavaScriptV3/kms-2014-11-01/Verify) + [AWS SDK for Kotlin](https://docs.aws.amazon.com/goto/SdkForKotlin/kms-2014-11-01/Verify) + [AWS SDK for PHP V3](https://docs.aws.amazon.com/goto/SdkForPHPV3/kms-2014-11-01/Verify) + [AWS SDK for Python](https://docs.aws.amazon.com/goto/boto3/kms-2014-11-01/Verify) + [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/kms-2014-11-01/Verify)