generateDataKeyWithoutPlaintext method

Future<GenerateDataKeyWithoutPlaintextResponse> generateDataKeyWithoutPlaintext({ required String keyId, bool? dryRun, Map<String, String>? encryptionContext, List<String>? grantTokens, DataKeySpec? keySpec, int? numberOfBytes, })

Returns a unique symmetric data key for use outside of KMS. This operation returns a data key that is encrypted under a symmetric encryption KMS key that you specify. The bytes in the key are random; they are not related to the caller or to the KMS key.

GenerateDataKeyWithoutPlaintext is identical to the GenerateDataKey operation except that it does not return a plaintext copy of the data key.

This operation is useful for systems that need to encrypt data at some point, but not immediately. When you need to encrypt the data, you call the Decrypt operation on the encrypted copy of the key.

It's also useful in distributed systems with different levels of trust. For example, you might store encrypted data in containers. One component of your system creates new containers and stores an encrypted data key with each container. Then, a different component puts the data into the containers. That component first decrypts the data key, uses the plaintext data key to encrypt data, puts the encrypted data into the container, and then destroys the plaintext data key. In this system, the component that creates the containers never sees the plaintext data key.

To request an asymmetric data key pair, use the GenerateDataKeyPair or GenerateDataKeyPairWithoutPlaintext operations.

To generate a data key, you must specify the symmetric encryption KMS key that is used to encrypt the data key. You cannot use an asymmetric KMS key or a key in a custom key store to generate a data key. To get the type of your KMS key, use the DescribeKey operation.

You must also specify the length of the data key. Use either the KeySpec or NumberOfBytes parameters (but not both). For 128-bit and 256-bit data keys, use the KeySpec parameter.

To generate an SM4 data key (China Regions only), specify a KeySpec value of AES_128 or NumberOfBytes value of 16. The symmetric encryption key used in China Regions to encrypt your data key is an SM4 encryption key.

If the operation succeeds, you will find the encrypted copy of the data key in the CiphertextBlob field.

You can use an optional encryption context to add additional security to the encryption operation. If you specify an EncryptionContext, you must specify the same encryption context (a case-sensitive exact match) when decrypting the encrypted data key. Otherwise, the request to decrypt fails with an InvalidCiphertextException. For more information, see Encryption Context 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 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:GenerateDataKeyWithoutPlaintext (key policy)

Related operations:

• Decrypt
• Encrypt
• GenerateDataKey
• GenerateDataKeyPair
• GenerateDataKeyPairWithoutPlaintext

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

May throw DependencyTimeoutException. May throw DisabledException. May throw DryRunOperationException. May throw InvalidGrantTokenException. May throw InvalidKeyUsageException. May throw KeyUnavailableException. May throw KMSInternalException. May throw KMSInvalidStateException. May throw NotFoundException.

Parameter keyId : Specifies the symmetric encryption KMS key that encrypts the data key. You cannot specify an asymmetric KMS key or a KMS key in a custom key store. To get the type and origin of your KMS key, use the DescribeKey operation.

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 Amazon Web Services 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 or DescribeKey. To get the alias name and alias ARN, use ListAliases.

Parameter dryRun : Checks if your request will succeed. DryRun is an optional parameter.

To learn more about how to use this parameter, see Testing your permissions in the Key Management Service Developer Guide.

Parameter encryptionContext : Specifies the encryption context that will be used when encrypting the data key. An encryption context is a collection of non-secret key-value pairs that represent additional authenticated data. When you use an encryption context to encrypt data, you must specify the same (an exact case-sensitive match) encryption context to decrypt the data. An encryption context is supported only on operations with symmetric encryption KMS keys. On operations with symmetric encryption KMS keys, an encryption context is optional, but it is strongly recommended.

For more information, see Encryption context in the Key Management Service Developer Guide.

Parameter grantTokens : 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 and Using a grant token in the Key Management Service Developer Guide.

Parameter keySpec : The length of the data key. Use AES_128 to generate a 128-bit symmetric key, or AES_256 to generate a 256-bit symmetric key.

Parameter numberOfBytes : The length of the data key in bytes. For example, use the value 64 to generate a 512-bit data key (64 bytes is 512 bits). For common key lengths (128-bit and 256-bit symmetric keys), we recommend that you use the KeySpec field instead of this one.

Implementation

Future<GenerateDataKeyWithoutPlaintextResponse>
    generateDataKeyWithoutPlaintext({
  required String keyId,
  bool? dryRun,
  Map<String, String>? encryptionContext,
  List<String>? grantTokens,
  DataKeySpec? keySpec,
  int? numberOfBytes,
}) async {
  _s.validateNumRange(
    'numberOfBytes',
    numberOfBytes,
    1,
    1024,
  );
  final headers = <String, String>{
    'Content-Type': 'application/x-amz-json-1.1',
    'X-Amz-Target': 'TrentService.GenerateDataKeyWithoutPlaintext'
  };
  final jsonResponse = await _protocol.send(
    method: 'POST',
    requestUri: '/',
    exceptionFnMap: _exceptionFns,
    // TODO queryParams
    headers: headers,
    payload: {
      'KeyId': keyId,
      if (dryRun != null) 'DryRun': dryRun,
      if (encryptionContext != null) 'EncryptionContext': encryptionContext,
      if (grantTokens != null) 'GrantTokens': grantTokens,
      if (keySpec != null) 'KeySpec': keySpec.value,
      if (numberOfBytes != null) 'NumberOfBytes': numberOfBytes,
    },
  );

  return GenerateDataKeyWithoutPlaintextResponse.fromJson(jsonResponse.body);
}