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.

GenerateDataKeyPair also supports Amazon Web Services Nitro Enclaves, which provide an isolated compute environment in Amazon EC2. To call GenerateDataKeyPair for an Amazon Web Services Nitro enclave, use the Amazon Web Services Nitro Enclaves SDK or any Amazon Web Services SDK. Use the Recipient parameter to provide the attestation document for the enclave. GenerateDataKeyPair returns the public data key and a copy of the private data key encrypted under the specified KMS key, as usual. But instead of a plaintext copy of the private data key ( PrivateKeyPlaintext), the response includes a copy of the private data key encrypted under the public key from the attestation document ( CiphertextForRecipient). For information about the interaction between KMS and Amazon Web Services Nitro Enclaves, see How Amazon Web Services Nitro Enclaves uses KMS in the Key Management Service Developer Guide..

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',
    ],
    Recipient={
        'KeyEncryptionAlgorithm': 'RSAES_OAEP_SHA_256',
        'AttestationDocument': b'bytes'
    },
    DryRun=True|False
)
Parameters:

  • EncryptionContext (dict) –

    Specifies the encryption context that will be used when encrypting the private key in the data key pair.

    Warning

    Do not include confidential or sensitive information in this field. This field may be displayed in plaintext in CloudTrail logs and other output.

    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) –

  • Recipient (dict) –

    A signed attestation document from an Amazon Web Services Nitro enclave and the encryption algorithm to use with the enclave’s public key. The only valid encryption algorithm is RSAES_OAEP_SHA_256.

    This parameter only supports attestation documents for Amazon Web Services Nitro Enclaves. To include this parameter, use the Amazon Web Services Nitro Enclaves SDK or any Amazon Web Services SDK.

    When you use this parameter, instead of returning a plaintext copy of the private data key, KMS encrypts the plaintext private data key under the public key in the attestation document, and returns the resulting ciphertext in the CiphertextForRecipient field in the response. This ciphertext can be decrypted only with the private key in the enclave. The CiphertextBlob field in the response contains a copy of the private data key encrypted under the KMS key specified by the KeyId parameter. The PrivateKeyPlaintext field in the response is null or empty.

    For information about the interaction between KMS and Amazon Web Services Nitro Enclaves, see How Amazon Web Services Nitro Enclaves uses KMS in the Key Management Service Developer Guide.

    • KeyEncryptionAlgorithm (string) –

      The encryption algorithm that KMS should use with the public key for an Amazon Web Services Nitro Enclave to encrypt plaintext values for the response. The only valid value is RSAES_OAEP_SHA_256.

    • AttestationDocument (bytes) –

      The attestation document for an Amazon Web Services Nitro Enclave. This document includes the enclave’s public key.

  • DryRun (boolean) –

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

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

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',
    'CiphertextForRecipient': b'bytes'
}

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.

      If the response includes the CiphertextForRecipient field, the PrivateKeyPlaintext field is null or empty.

    • 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.

    • CiphertextForRecipient (bytes) –

      The plaintext private data key encrypted with the public key from the Nitro enclave. This ciphertext can be decrypted only by using a private key in the Nitro enclave.

      This field is included in the response only when the Recipient parameter in the request includes a valid attestation document from an Amazon Web Services Nitro enclave. For information about the interaction between KMS and Amazon Web Services Nitro Enclaves, see How Amazon Web Services Nitro Enclaves uses KMS in the Key Management Service Developer Guide.

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

  • KMS.Client.exceptions.DryRunOperationException

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': {
        '...': '...',
    },
}