verify

Verifies a digital signature that was generated by the Sign 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 in the 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 KMS. Use the GetPublicKey operation to download the public key in the asymmetric KMS key and then use the public key to verify the signature outside of KMS. The advantage of using the Verify operation is that it is performed within KMS. As a result, it's easy to call, the operation is performed within the FIPS boundary, it is logged in 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 KMS with an SM2 public key (China Regions only), you must specify the distinguishing ID. By default, KMS uses 1234567812345678 as the distinguishing ID. For more information, see Offline verification with SM2 key pairs.

The KMS key that you use for this operation must be in a compatible key state. For details, see Key states of KMS keys 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:Verify (key policy)

Related operations: Sign

Eventual consistency: The KMS API follows an eventual consistency model. For more information, see KMS eventual consistency.

Samples

import aws.sdk.kotlin.services.kms.model.MessageType
import aws.sdk.kotlin.services.kms.model.SigningAlgorithmSpec

fun main() { 
   //sampleStart 
   // This operation uses the public key in an elliptic curve (ECC) asymmetric key to verify a digital
// signature within AWS KMS.
val resp = kmsClient.verify {
    keyId = "alias/ECC_signing_key"
    message = "<message to be verified>".encodeAsByteArray()
    messageType = MessageType.fromValue("RAW")
    signature = "<binary data>".encodeAsByteArray()
    signingAlgorithm = SigningAlgorithmSpec.fromValue("ECDSA_SHA_384")
} 
   //sampleEnd
}

import aws.sdk.kotlin.services.kms.model.MessageType
import aws.sdk.kotlin.services.kms.model.SigningAlgorithmSpec

fun main() { 
   //sampleStart 
   // This operation uses the public key in an RSA asymmetric signing key pair to verify the digital
// signature of a message digest. Hashing a message into a digest before sending it to KMS lets you verify
// messages that exceed the 4096 byte message size limit. To indicate that the value of Message is a digest,
// use the MessageType parameter
val resp = kmsClient.verify {
    keyId = "arn:aws:kms:us-east-2:111122223333:key/0987dcba-09fe-87dc-65ba-ab0987654321"
    message = "<message digest to be verified>".encodeAsByteArray()
    messageType = MessageType.fromValue("DIGEST")
    signature = "<binary data>".encodeAsByteArray()
    signingAlgorithm = SigningAlgorithmSpec.fromValue("RSASSA_PSS_SHA_512")
} 
   //sampleEnd
}