# Use `Verify` with an AWS SDK or CLI
<a name="example_kms_Verify_section"></a>

The following code examples show how to use `Verify`.

------
#### [ CLI ]

**AWS CLI**  
**To verify a digital signature**  
The following `verify` command verifies a cryptographic signature for a short, Base64-encoded message. The key ID, message, message type, and signing algorithm must be same ones that were used to sign the message.  
In AWS CLI v2, the value of the `message` parameter must be Base64-encoded. Or, you can save the message in a file and use the `fileb://` prefix, which tells the AWS CLI to read binary data from the file.  
The signature that you specify cannot be base64-encoded. For help decoding the signature that the `sign` command returns, see the `sign` command examples.  
The output of the command includes a Boolean `SignatureValid` field that indicates that the signature was verified. If the signature validation fails, the `verify` command fails, too.  
Before running this command, replace the example key ID with a valid key ID from your AWS account.  

```
aws kms verify \
    --key-id 1234abcd-12ab-34cd-56ef-1234567890ab \
    --message fileb://EncodedMessage \
    --message-type RAW \
    --signing-algorithm RSASSA_PKCS1_V1_5_SHA_256 \
    --signature fileb://ExampleSignature
```
Output:  

```
{
    "KeyId": "arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab",
    "SignatureValid": true,
    "SigningAlgorithm": "RSASSA_PKCS1_V1_5_SHA_256"
}
```
For more information about using asymmetric KMS keys in AWS KMS, see [Using asymmetric keys](https://docs.aws.amazon.com/kms/latest/developerguide/symmetric-asymmetric.html) in the *AWS Key Management Service Developer Guide*.  
+  For API details, see [Verify](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/kms/verify.html) in *AWS CLI Command Reference*. 

------
#### [ Python ]

**SDK for Python (Boto3)**  
 There's more on GitHub. Find the complete example and learn how to set up and run in the [AWS Code Examples Repository](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/python/example_code/kms#code-examples). 

```
class KeyEncrypt:
    def __init__(self, kms_client):
        self.kms_client = kms_client

    @classmethod
    def from_client(cls) -> "KeyEncrypt":
        """
        Creates a KeyEncrypt instance with a default KMS client.

        :return: An instance of KeyEncrypt initialized with the default KMS client.
        """
        kms_client = boto3.client("kms")
        return cls(kms_client)


    def verify(self, key_id: str, message: str, signature: str) -> bool:
        """
        Verifies a signature against a message.

        :param key_id: The ARN or ID of the key used to sign the message.
        :param message: The message to verify.
        :param signature: The signature to verify.
        :return: True when the signature matches the message, otherwise False.
        """
        try:
            response = self.kms_client.verify(
                KeyId=key_id,
                Message=message.encode(),
                Signature=signature,
                SigningAlgorithm="RSASSA_PSS_SHA_256",
            )
            valid = response["SignatureValid"]
            print(f"The signature is {'valid' if valid else 'invalid'}.")
            return valid
        except ClientError as err:
            if err.response["Error"]["Code"] == "SignatureDoesNotMatchException":
                print("The signature is not valid.")
            else:
                logger.error(
                    "Couldn't verify your signature. Here's why: %s",
                    err.response["Error"]["Message"],
                )
            raise
```
+  For API details, see [Verify](https://docs.aws.amazon.com/goto/boto3/kms-2014-11-01/Verify) in *AWS SDK for Python (Boto3) API Reference*. 

------
#### [ SAP ABAP ]

**SDK for SAP ABAP**  
 There's more on GitHub. Find the complete example and learn how to set up and run in the [AWS Code Examples Repository](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/sap-abap/services/kms#code-examples). 

```
    TRY.
        " iv_key_id = 'arn:aws:kms:us-east-1:123456789012:key/1234abcd-12ab-34cd-56ef-1234567890ab' (asymmetric key)
        " iv_message contains the original message
        " iv_signature contains the signature to verify
        " iv_signing_algorithm = 'RSASSA_PSS_SHA_256'
        oo_result = lo_kms->verify(
          iv_keyid = iv_key_id
          iv_message = iv_message
          iv_signature = iv_signature
          iv_signingalgorithm = iv_signing_algorithm
        ).
        DATA(lv_valid) = oo_result->get_signaturevalid( ).
        IF lv_valid = abap_true.
          MESSAGE 'Signature is valid.' TYPE 'I'.
        ELSE.
          MESSAGE 'Signature is invalid.' TYPE 'I'.
        ENDIF.
      CATCH /aws1/cx_kmsdisabledexception.
        MESSAGE 'The key is disabled.' TYPE 'E'.
      CATCH /aws1/cx_kmsnotfoundexception.
        MESSAGE 'Key not found.' TYPE 'E'.
      CATCH /aws1/cx_kmskmsinvalidsigex.
        MESSAGE 'Invalid signature.' TYPE 'E'.
      CATCH /aws1/cx_kmskmsinternalex.
        MESSAGE 'An internal error occurred.' TYPE 'E'.
    ENDTRY.
```
+  For API details, see [Verify](https://docs.aws.amazon.com/sdk-for-sap-abap/v1/api/latest/index.html) in *AWS SDK for SAP ABAP API reference*. 

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For a complete list of AWS SDK developer guides and code examples, see [Using this service with an AWS SDK](sdk-general-information-section.md). This topic also includes information about getting started and details about previous SDK versions.