KMS / Client / generate_data_key_pair

generate_data_key_pair#

KMS.Client.generate_data_key_pair(**kwargs)#

Returns a unique asymmetric data key pair for use outside of KMS. This operation returns a plaintext public key, a plaintext private key, and a copy of the private key that is encrypted under the symmetric encryption KMS key you specify. You can use the data key pair to perform asymmetric cryptography and implement digital signatures outside of KMS. The bytes in the keys are random; they not related to the caller or to the KMS key that is used to encrypt the private key.

You can use the public key that GenerateDataKeyPair returns to encrypt data or verify a signature outside of KMS. Then, store the encrypted private key with the data. When you are ready to decrypt data or sign a message, you can use the Decrypt operation to decrypt the encrypted private key.

To generate a data key pair, you must specify a symmetric encryption KMS key to encrypt the private key in a data key pair. You cannot use 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.

Use the KeyPairSpec parameter to choose an RSA or Elliptic Curve (ECC) data key pair. In China Regions, you can also choose an SM2 data key pair. KMS recommends that you use ECC key pairs for signing, and use RSA and SM2 key pairs for either encryption or signing, but not both. However, KMS cannot enforce any restrictions on the use of data key pairs outside of KMS.

If you are using the data key pair to encrypt data, or for any operation where you don’t immediately need a private key, consider using the GenerateDataKeyPairWithoutPlaintext operation. GenerateDataKeyPairWithoutPlaintext returns a plaintext public key and an encrypted private key, but omits the plaintext private key that you need only to decrypt ciphertext or sign a message. Later, when you need to decrypt the data or sign a message, use the Decrypt operation to decrypt the encrypted private key in the data key pair.

GenerateDataKeyPair returns a unique data key pair for each request. The bytes in the keys are random; they are not related to the caller or the KMS key that is used to encrypt the private key. The public key is a DER-encoded X.509 SubjectPublicKeyInfo, as specified in RFC 5280. The private key is a DER-encoded PKCS8 PrivateKeyInfo, as specified in RFC 5958.

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:GenerateDataKeyPair (key policy)

Related operations:

Decrypt
Encrypt
GenerateDataKey
GenerateDataKeyPairWithoutPlaintext
GenerateDataKeyWithoutPlaintext

See also: AWS API Documentation

Request Syntax

response = client.generate_data_key_pair(
    EncryptionContext={
        'string': 'string'
    },
    KeyId='string',
    KeyPairSpec='RSA_2048'|'RSA_3072'|'RSA_4096'|'ECC_NIST_P256'|'ECC_NIST_P384'|'ECC_NIST_P521'|'ECC_SECG_P256K1'|'SM2',
    GrantTokens=[
        'string',
    ]
)

Parameters:

EncryptionContext (dict) –
Specifies the encryption context that will be used when encrypting the private key in the data key pair.

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.
- (string) –
  - (string) –
KeyId (string) –
[REQUIRED]

Specifies the symmetric encryption KMS key that encrypts the private key in the data key pair. 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.
KeyPairSpec (string) –
[REQUIRED]

Determines the type of data key pair that is generated.

The KMS rule that restricts the use of asymmetric RSA and SM2 KMS keys to encrypt and decrypt or to sign and verify (but not both), and the rule that permits you to use ECC KMS keys only to sign and verify, are not effective on data key pairs, which are used outside of KMS. The SM2 key spec is only available in China Regions.
GrantTokens (list) –
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.
- (string) –

Return type:

dict

Returns:

Response Syntax

{
    'PrivateKeyCiphertextBlob': b'bytes',
    'PrivateKeyPlaintext': b'bytes',
    'PublicKey': b'bytes',
    'KeyId': 'string',
    'KeyPairSpec': 'RSA_2048'|'RSA_3072'|'RSA_4096'|'ECC_NIST_P256'|'ECC_NIST_P384'|'ECC_NIST_P521'|'ECC_SECG_P256K1'|'SM2'
}

Response Structure

(dict) –
- PrivateKeyCiphertextBlob (bytes) –
  
  The encrypted copy of the private key. When you use the HTTP API or the Amazon Web Services CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded.
- PrivateKeyPlaintext (bytes) –
  
  The plaintext copy of the private key. When you use the HTTP API or the Amazon Web Services CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded.
- PublicKey (bytes) –
  
  The public key (in plaintext). When you use the HTTP API or the Amazon Web Services CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded.
- KeyId (string) –
  
  The Amazon Resource Name ( key ARN) of the KMS key that encrypted the private key.
- KeyPairSpec (string) –
  
  The type of data key pair that was generated.

Exceptions

KMS.Client.exceptions.NotFoundException
KMS.Client.exceptions.DisabledException
KMS.Client.exceptions.KeyUnavailableException
KMS.Client.exceptions.DependencyTimeoutException
KMS.Client.exceptions.InvalidKeyUsageException
KMS.Client.exceptions.InvalidGrantTokenException
KMS.Client.exceptions.KMSInternalException
KMS.Client.exceptions.KMSInvalidStateException
KMS.Client.exceptions.UnsupportedOperationException

Examples

This example generates an RSA data key pair for encryption and decryption. The operation returns a plaintext public key and private key, and a copy of the private key that is encrypted under a symmetric encryption KMS key that you specify.

response = client.generate_data_key_pair(
    # The key ID of the symmetric encryption KMS key that encrypts the private RSA key in the data key pair.
    KeyId='arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab',
    # The requested key spec of the RSA data key pair.
    KeyPairSpec='RSA_3072',
)

print(response)

Expected Output:

{
    # The key ARN of the symmetric encryption KMS key that was used to encrypt the private key.
    'KeyId': 'arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab',
    # The actual key spec of the RSA data key pair.
    'KeyPairSpec': 'RSA_3072',
    # The encrypted private key of the RSA data key pair.
    'PrivateKeyCiphertextBlob': '<binary data>',
    # The plaintext private key of the RSA data key pair.
    'PrivateKeyPlaintext': '<binary data>',
    # The public key (plaintext) of the RSA data key pair.
    'PublicKey': '<binary data>',
    'ResponseMetadata': {
        '...': '...',
    },
}