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[ aws . kms ]

verify

Description

Verifies a digital signature that was generated by the Sign operation.

Verification confirms that an authorized user signed the message with the specified CMK 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 CMK. The signature is verified by using the public key in the same asymmetric CMK. For information about symmetric and asymmetric CMKs, see Using Symmetric and Asymmetric CMKs in the AWS Key Management Service Developer Guide .

To verify a digital signature, you can use the Verify operation. Specify the same asymmetric CMK, message, and signing algorithm that were used to produce the signature.

You can also verify the digital signature by using the public key of the CMK outside of AWS KMS. Use the GetPublicKey operation to download the public key in the asymmetric CMK 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 CMK to verify signatures.

The CMK that you use for this operation must be in a compatible key state. For details, see How Key State Affects Use of a Customer Master Key in the AWS Key Management Service Developer Guide .

See also: AWS API Documentation

See 'aws help' for descriptions of global parameters.

Synopsis

  verify
--key-id <value>
--message <value>
[--message-type <value>]
--signature <value>
--signing-algorithm <value>
[--grant-tokens <value>]
[--cli-input-json <value>]
[--generate-cli-skeleton <value>]

Options

--key-id (string)

Identifies the asymmetric CMK that will be used to verify the signature. This must be the same CMK that was used to generate the signature. If you specify a different CMK, the signature verification fails.

To specify a CMK, use its key ID, Amazon Resource Name (ARN), alias name, or alias ARN. When using an alias name, prefix it with "alias/" . To specify a CMK 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 CMK, use ListKeys or DescribeKey . To get the alias name and alias ARN, use ListAliases .

--message (blob)

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.

--message-type (string)

Tells AWS KMS whether the value of the Message parameter is a message or message digest. The default value, RAW, indicates a message. To indicate a message digest, enter DIGEST .

Warning

Use the DIGEST value only when the value of the Message parameter is a message digest. If you use the DIGEST value with a raw message, the security of the verification operation can be compromised.

Possible values:

  • RAW
  • DIGEST

--signature (blob)

The signature that the Sign operation generated.

--signing-algorithm (string)

The signing algorithm that was used to sign the message. If you submit a different algorithm, the signature verification fails.

Possible 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

--grant-tokens (list)

A list of grant tokens.

For more information, see Grant Tokens in the AWS Key Management Service Developer Guide .

(string)

Syntax:

"string" "string" ...

--cli-input-json (string) Performs service operation based on the JSON string provided. The JSON string follows the format provided by --generate-cli-skeleton. If other arguments are provided on the command line, the CLI values will override the JSON-provided values. It is not possible to pass arbitrary binary values using a JSON-provided value as the string will be taken literally.

--generate-cli-skeleton (string) Prints a JSON skeleton to standard output without sending an API request. If provided with no value or the value input, prints a sample input JSON that can be used as an argument for --cli-input-json. If provided with the value output, it validates the command inputs and returns a sample output JSON for that command.

See 'aws help' for descriptions of global parameters.

Examples

To verify a digital signature

The following verify example verifies a cryptographic signature for a short message. The key ID, message, message type, and signing algorithm must be same ones that were used to sign the message. 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://originalString \
    --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 CMKs in AWS KMS, see Using Symmetric and Asymmetric Keys in the AWS Key Management Service API Reference.

Output

KeyId -> (string)

The Amazon Resource Name (key ARN ) of the asymmetric CMK that was used to verify the signature.

SignatureValid -> (boolean)

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.

SigningAlgorithm -> (string)

The signing algorithm that was used to verify the signature.