GenerateDataKeyWithoutPlaintext
Returns a unique symmetric data key for use outside of Amazon KMS. This operation returns a data key that is encrypted under a symmetric encryption KMS key that you specify. The bytes in the key are random; they are not related to the caller or to the KMS key.
GenerateDataKeyWithoutPlaintext
is identical to the GenerateDataKey operation except that it does not return a plaintext 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.
To request an asymmetric data key pair, use the GenerateDataKeyPair or GenerateDataKeyPairWithoutPlaintext operations.
To generate a data key, you must specify the symmetric encryption KMS key that is used to encrypt the data key. You cannot use an asymmetric KMS key or a key in a custom key store to generate a data key. To get the type of your KMS key, 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 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
Amazon 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 Amazon KMS keys in the Amazon 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: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
-
Specifies the symmetric encryption KMS key that encrypts the data key. 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.
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 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 Amazon 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 and Using a grant token in the Amazon 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 Amazon 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 KMS key 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 KMS key 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 KMS key 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 KMS key
(KeySpec
).
For encrypting, decrypting, re-encrypting, and generating data keys, the
KeyUsage
must beENCRYPT_DECRYPT
. For signing and verifying messages, theKeyUsage
must beSIGN_VERIFY
. For generating and verifying message authentication codes (MACs), theKeyUsage
must beGENERATE_VERIFY_MAC
. To find theKeyUsage
of a KMS key, use the DescribeKey operation.To find the encryption or signing algorithms supported for a particular KMS key, use the DescribeKey operation.
HTTP Status Code: 400
-
- KeyUnavailableException
-
The request was rejected because the specified KMS key 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 KMS key, see Key states of Amazon KMS keys in the Amazon 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 Amazon SDKs, see the following: