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:GenerateDataKey

Last Updated:Dec 18, 2023

Generates a random data key that is used to encrypt on-premises data.

This operation creates a random data key, encrypts the data key by using a key, and returns the plaintext and ciphertext of the data key. You can use the data key plaintext to encrypt on-premises data without using Key Management Service (KMS). You must store the data ciphertext together with the data key ciphertext. You can obtain the data key plaintext from the Plaintext parameter in the response and the data key ciphertext from the CiphertextBlob parameter in the response.

The key that you specify in the request is only used to encrypt the data key and is not involved in the generation of the data key. KMS does not record or store the data key. Therefore, you must store the data key ciphertext in persistent storage.

We recommend that you encrypt on-premises data by performing the following steps:

1. Call the GenerateDataKey operation.

2. Use the data key plaintext that you obtain to encrypt on-premises data without using KMS. Then, delete the data key plaintext from the memory.

3. Store the data ciphertext together with the data key ciphertext that you obtain.

We recommend that you decrypt on-premises data by performing the following steps:

  • Call the Decrypt operation to decrypt the locally stored data key ciphertext. The data key plaintext is returned.

  • Use the data key plaintext to decrypt on-premises data and then delete the data key plaintext from the memory.

In this example, a random data key is generated for a key whose ID is 7906979c-8e06-46a2-be2d-68e3ccbc****.

Debugging

OpenAPI Explorer automatically calculates the signature value. For your convenience, we recommend that you call this operation in OpenAPI Explorer. OpenAPI Explorer dynamically generates the sample code of the operation for different SDKs.

Request parameters

Parameter

Type

Required

Example

Description

Action

String

Yes

GenerateDataKey

The operation that you want to perform. Set the value to GenerateDataKey.

KeyId

String

Yes

7906979c-8e06-46a2-be2d-68e3ccbc****

The ID of the key. The ID must be globally unique.

You can also set this parameter to an alias that is bound to the key. For more information, see Alias overview.

KeySpec

String

No

AES_256

The type of the data key that you want to generate. Valid values:

  • AES_256: a 256-bit symmetric key

  • AES_128: a 128-bit symmetric key

Note

We recommend that you use the KeySpec or NumberOfBytes parameter to specify the length of a data key. If none of the parameters are specified, KMS generates a 256-bit data key. If both parameters are specified, KMS ignores the KeySpec parameter.

NumberOfBytes

Integer

No

256

The length of the data key that you want to generate. Unit: bytes.

Valid values: 1 to 1024.

Default values:

  • If the KeySpec parameter is set to AES_256, set the value of the NumberOfBytes parameter to 32.

  • If the KeySpec parameter is set to AES_128, set the value of the NumberOfBytes parameter to 16.

EncryptionContext

Map

No

{"Example":"Example"}

The JSON string that consists of key-value pairs.

If you configure this parameter, you must configure the same parameter when you call the Decrypt operation. For more information, see EncryptionContext.

For more information about common request parameters, see Common parameters.

Response parameters

Parameter

Type

Example

Description

KeyVersionId

String

2ab1a983-7072-4bbc-a582-584b5bd8****

The ID of the key version. The ID must be globally unique.

KeyId

String

7906979c-8e06-46a2-be2d-68e3ccbc****

The ID of the key. The ID must be globally unique.

Note

If you set the KeyId parameter in the request to an alias of the key, the ID of the key to which the alias is bound is returned.

CiphertextBlob

String

ODZhOWVmZDktM2QxNi00ODk0LWJkNGYtMWZjNDNmM2YyYWJmS7FmDBBQ0BkKsQrtRnidtPwirmDcS0ZuJCU41xxAAWk4Z8qsADfbV0b+i6kQmlvj79dJdGOvtX69Uycs901qOjop4bTS****

The data key ciphertext that is encrypted by using the primary version of the key.

RequestId

String

7021b6ec-4be7-4d3c-8a68-1e85d4d515a0

The ID of the request, which is used to locate and troubleshoot issues.

Plaintext

String

QmFzZTY0IGVuY29kZWQgcGxhaW50****

The Base64 encoded data key plaintext.

Examples

Sample requests

http(s)://[Endpoint]/?Action=GenerateDataKey
&KeyId=7906979c-8e06-46a2-be2d-68e3ccbc****
&KeySpec=AES_256
&NumberOfBytes=256
&<Common request parameters>

Sample success responses

XML format

HTTP/1.1 200 OK
Content-Type:application/xml

<GenerateDataKeyResponse>
    <KeyVersionId>2ab1a983-7072-4bbc-a582-584b5bd8****</KeyVersionId>
    <KeyId>7906979c-8e06-46a2-be2d-68e3ccbc****</KeyId>
    <CiphertextBlob>ODZhOWVmZDktM2QxNi00ODk0LWJkNGYtMWZjNDNmM2YyYWJmS7FmDBBQ0BkKsQrtRnidtPwirmDcS0ZuJCU41xxAAWk4Z8qsADfbV0b+i6kQmlvj79dJdGOvtX69Uycs901qOjop4bTS****</CiphertextBlob>
    <RequestId>7021b6ec-4be7-4d3c-8a68-1e85d4d515a0</RequestId>
    <Plaintext>QmFzZTY0IGVuY29kZWQgcGxhaW50****</Plaintext>
</GenerateDataKeyResponse>

JSON format

HTTP/1.1 200 OK
Content-Type:application/json

{
  "KeyVersionId" : "2ab1a983-7072-4bbc-a582-584b5bd8****",
  "KeyId" : "7906979c-8e06-46a2-be2d-68e3ccbc****",
  "CiphertextBlob" : "ODZhOWVmZDktM2QxNi00ODk0LWJkNGYtMWZjNDNmM2YyYWJmS7FmDBBQ0BkKsQrtRnidtPwirmDcS0ZuJCU41xxAAWk4Z8qsADfbV0b+i6kQmlvj79dJdGOvtX69Uycs901qOjop4bTS****",
  "RequestId" : "7021b6ec-4be7-4d3c-8a68-1e85d4d515a0",
  "Plaintext" : "QmFzZTY0IGVuY29kZWQgcGxhaW50****"
}

Error codes

HTTP status code

Error code

Error message

Description

400

UnsupportedOperation

This action is not supported.

The operation is not supported.

404

Forbidden.AliasNotFound

The specified Alias is not found.

The specified alias is not found.

404

Forbidden.KeyNotFound

The specified Key is not found.

The specified key does not exist.

409

Rejected.Disabled

The request was rejected because the key state is Disabled.

The request is denied because the key is disabled.

409

Rejected.PendingDeletion

The request was rejected because the key state is PendingDeletion.

The request is denied because the key is in the Pending Deletion state.

409

Rejected.Unavailable

The request was rejected because the key state is Unavailable.

The request is denied because the key is unavailable.

For a list of error codes, see Service error codes.