Key Management Service:GenerateDataKey

Usage notes

This API can be called through either a shared gateway or a dedicated gateway. For more information, see Alibaba Cloud SDK.

• Shared gateway: Accesses KMS through public network or VPC domain names, using one of the following formats:

  • Public network domain names: kms.<REGION_ID>.aliyuncs.com.

  • VPC domain names: kms-vpc.<REGION_ID>.aliyuncs.com.

  This method requires enabling public network access. For instructions, see Access KMS instance keys over the Internet.

• Dedicated gateway: Access KMS through the KMS private network domain names, following the format: <YOUR_KMS_INSTANCE_ID>.cryptoservice.kms.aliyuncs.com.

QPS Limits

• When calling this API through a shared gateway: The API is rate-limited to 1000 queries per second (QPS) per Alibaba Cloud account. Exceeding this limit will result in throttling, which may impact your service. We recommend that you take note of the limit when you call this operation.

• When calling this API through a dedicated gateway: The API's QPS limit per Alibaba Cloud account is determined by the compute performance specifications of your KMS instances. For more information on the compute performance specifications, see Performance quota.

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.