GenerateDataKeyWithoutPlaintext
Generates a unique symmetric data key. This operation returns a data key that is encrypted under a customer master key (CMK) that you specify. To request an asymmetric data key pair, use the GenerateDataKeyPair or GenerateDataKeyPairWithoutPlaintext operations.
GenerateDataKeyWithoutPlaintext
is identical to the GenerateDataKey operation except that returns only the encrypted copy of the
data key. This operation is useful for systems that need to encrypt data at some point,
but
not immediately. When you need to encrypt the data, you call the Decrypt
operation on the encrypted copy of the key.
It's also useful in distributed systems with different levels of trust. For example, you might store encrypted data in containers. One component of your system creates new containers and stores an encrypted data key with each container. Then, a different component puts the data into the containers. That component first decrypts the data key, uses the plaintext data key to encrypt data, puts the encrypted data into the container, and then destroys the plaintext data key. In this system, the component that creates the containers never sees the plaintext data key.
GenerateDataKeyWithoutPlaintext
returns a unique data key for each request.
The bytes in the keys are not related to the caller or CMK that is used to encrypt
the private
key.
To generate a data key, you must specify the symmetric customer master key (CMK) that is used to encrypt the data key. You cannot use an asymmetric CMK to generate a data key. To get the type of your CMK, use the DescribeKey operation.
If the operation succeeds, you will find the encrypted copy of the data key in the
CiphertextBlob
field.
You can use the 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
AWS Key Management Service Developer Guide.
The CMK that you use for this operation must be in a compatible key state. For details, see Key state: Effect on your CMK in the AWS Key Management Service Developer Guide.
Cross-account use: Yes. To perform this operation with a CMK in a different AWS account, specify
the key ARN or alias ARN in the value of the KeyId
parameter.
Required permissions: kms:GenerateDataKeyWithoutPlaintext (key policy)
Related operations:
Request Syntax
{
"EncryptionContext": {
"string
" : "string
"
},
"GrantTokens": [ "string
" ],
"KeyId": "string
",
"KeySpec": "string
",
"NumberOfBytes": number
}
Request Parameters
For information about the parameters that are common to all actions, see Common Parameters.
The request accepts the following data in JSON format.
In the following list, the required parameters are described first.
- KeyId
-
The identifier of the symmetric customer master key (CMK) that encrypts the data key.
To specify a CMK, use its key ID, Amazon Resource Name (ARN), alias name, or alias ARN. When using an alias name, prefix it with
"alias/"
. To specify a CMK in a different AWS 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 CMK, use ListKeys or DescribeKey. To get the alias name and alias ARN, use ListAliases.
Type: String
Length Constraints: Minimum length of 1. Maximum length of 2048.
Required: Yes
-
- EncryptionContext
-
Specifies the encryption context that will be used when encrypting the data key.
An encryption context is a collection of non-secret key-value pairs that represents 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 optional when encrypting with a symmetric CMK, but it is highly recommended.
For more information, see Encryption Context in the AWS Key Management Service Developer Guide.
Type: String to string map
Required: No
- GrantTokens
-
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 in the AWS Key Management Service Developer Guide.
Type: Array of strings
Array Members: Minimum number of 0 items. Maximum number of 10 items.
Length Constraints: Minimum length of 1. Maximum length of 8192.
Required: No
- KeySpec
-
The length of the data key. Use
AES_128
to generate a 128-bit symmetric key, orAES_256
to generate a 256-bit symmetric key.Type: String
Valid Values:
AES_256 | AES_128
Required: No
- NumberOfBytes
-
The length of the data key in bytes. For example, use the value 64 to generate a 512-bit data key (64 bytes is 512 bits). For common key lengths (128-bit and 256-bit symmetric keys), we recommend that you use the
KeySpec
field instead of this one.Type: Integer
Valid Range: Minimum value of 1. Maximum value of 1024.
Required: No
Response Syntax
{
"CiphertextBlob": blob,
"KeyId": "string"
}
Response Elements
If the action is successful, the service sends back an HTTP 200 response.
The following data is returned in JSON format by the service.
- CiphertextBlob
-
The encrypted data key. When you use the HTTP API or the AWS CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded.
Type: Base64-encoded binary data object
Length Constraints: Minimum length of 1. Maximum length of 6144.
- KeyId
-
The Amazon Resource Name (key ARN) of the CMK that encrypted the data key.
Type: String
Length Constraints: Minimum length of 1. Maximum length of 2048.
Errors
For information about the errors that are common to all actions, see Common Errors.
- DependencyTimeoutException
-
The system timed out while trying to fulfill the request. The request can be retried.
HTTP Status Code: 500
- DisabledException
-
The request was rejected because the specified CMK is not enabled.
HTTP Status Code: 400
- InvalidGrantTokenException
-
The request was rejected because the specified grant token is not valid.
HTTP Status Code: 400
- InvalidKeyUsageException
-
The request was rejected for one of the following reasons:
-
The
KeyUsage
value of the CMK is incompatible with the API operation. -
The encryption algorithm or signing algorithm specified for the operation is incompatible with the type of key material in the CMK
(CustomerMasterKeySpec
).
For encrypting, decrypting, re-encrypting, and generating data keys, the
KeyUsage
must beENCRYPT_DECRYPT
. For signing and verifying, theKeyUsage
must beSIGN_VERIFY
. To find theKeyUsage
of a CMK, use the DescribeKey operation.To find the encryption or signing algorithms supported for a particular CMK, use the DescribeKey operation.
HTTP Status Code: 400
-
- KeyUnavailableException
-
The request was rejected because the specified CMK was not available. You can retry the request.
HTTP Status Code: 500
- KMSInternalException
-
The request was rejected because an internal exception occurred. The request can be retried.
HTTP Status Code: 500
- KMSInvalidStateException
-
The request was rejected because the state of the specified resource is not valid for this request.
For more information about how key state affects the use of a CMK, see How Key State Affects Use of a Customer Master Key in the AWS Key Management Service Developer Guide .
HTTP Status Code: 400
- NotFoundException
-
The request was rejected because the specified entity or resource could not be found.
HTTP Status Code: 400
Examples
The following examples are formatted for legibility.
Example Request
This example illustrates one usage of GenerateDataKeyWithoutPlaintext.
POST / HTTP/1.1 Host: kms.us-east-2.amazonaws.com Content-Length: 50 X-Amz-Target: TrentService.GenerateDataKeyWithoutPlaintext X-Amz-Date: 20161112T001941Z Content-Type: application/x-amz-json-1.1 Authorization: AWS4-HMAC-SHA256\ Credential=AKIAI44QH8DHBEXAMPLE/20161112/us-east-2/kms/aws4_request,\ SignedHeaders=content-type;host;x-amz-date;x-amz-target,\ Signature=c86e7fc0218461e537c0d06ac29d865d94dba6fbfad00a844f61200e651df483 { "KeyId": "alias/ExampleAlias", "KeySpec": "AES_256" }
Example Response
This example illustrates one usage of GenerateDataKeyWithoutPlaintext.
HTTP/1.1 200 OK Server: Server Date: Sat, 12 Nov 2016 00:19:41 GMT Content-Type: application/x-amz-json-1.1 Content-Length: 331 Connection: keep-alive x-amzn-RequestId: b4ca7ee7-a86d-11e6-8a4e-2f341b963ed6 { "CiphertextBlob": "AQEDAHjRYf5WytIc0C857tFSnBaPn2F8DgfmThbJlGfR8P3WlwAAAH4wfAYJKoZIhvcNAQcGoG8wbQIBADBoBgkqhkiG9w0BBwEwHgYJYIZIAWUDBAEuMBEEDEvihQE/ntdQTL16wQIBEIA7BE/3LB7F1meU8z4e1vEKBGZgXPwMvkZXbKnf3wxCD9lB4hU29lii4euOqxp8pESb+7oCN9f1R75ac3s=", "KeyId": "arn:aws:kms:us-east-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab" }
See Also
For more information about using this API in one of the language-specific AWS SDKs, see the following: