Key Management Service：GenerateDataKey

Usage notes

• Keys outside Key Management Service (KMS) instances: To perform cryptographic operations, use Alibaba Cloud SDK to call operations.
• Keys in KMS instances: To perform cryptographic operations, use one of the following methods:
  • Method 1 (recommended): Use KMS Instance SDK to call KMS Instance API operations. For more information, see KMS Instance SDK and KMS Instance API.
  • Method 2: Use Alibaba Cloud SDK to call operations. The authentication method supports only Resource Access Management (RAM) roles whose trusted entities are Alibaba Cloud services. For more information, see Create a RAM role for a trusted Alibaba Cloud service.

Limits

You can call this operation up to 750 times per second per account. If the number of calls per second exceeds the limit, throttling is triggered. As a result, your business may be affected. We recommend that you take note of the limit when you call this operation.

Description

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 KMS. You must store the data ciphertext together with the data key ciphertext. You can obtain the data key plaintext from Plaintext in the response and the data key ciphertext from CiphertextBlob in the response.

The key that you specify in the request is used to only 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 to obtain a data key that is used for data encryption.

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 key-hzz630494463ejqjx****.

Request parameters

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

Response parameters

Examples

Sample requests

http(s)://[Endpoint]/?Action=GenerateDataKey
&KeyId=key-hzz630494463ejqjx****
&KeySpec=AES_256
&NumberOfBytes=256
&DryRun=false
&<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>key-hzz630494463ejqjx****</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" : "key-hzz630494463ejqjx****",
  "CiphertextBlob" : "ODZhOWVmZDktM2QxNi00ODk0LWJkNGYtMWZjNDNmM2YyYWJmS7FmDBBQ0BkKsQrtRnidtPwirmDcS0ZuJCU41xxAAWk4Z8qsADfbV0b+i6kQmlvj79dJdGOvtX69Uycs901qOjop4bTS****",
  "RequestId" : "7021b6ec-4be7-4d3c-8a68-1e85d4d515a0",
  "Plaintext" : "QmFzZTY0IGVuY29kZWQgcGxhaW50****"
}

Error codes

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