Generate Data Key Without Plaintext
kms_generate_data_key_without_plaintext | R Documentation |
Returns a unique symmetric data key for use outside of KMS¶
Description¶
Returns a unique symmetric data key for use outside of 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.
generate_data_key_without_plaintext
is identical to the
generate_data_key
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 generate_data_key_pair
or generate_data_key_pair_without_plaintext
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 describe_key
operation.
You must also specify the length of the data key. Use either the
KeySpec
or NumberOfBytes
parameters (but not both). For 128-bit and
256-bit data keys, use the KeySpec
parameter.
To generate an SM4 data key (China Regions only), specify a KeySpec
value of AES_128
or NumberOfBytes
value of 16
. The symmetric
encryption key used in China Regions to encrypt your data key is an SM4
encryption key.
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 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 KMS keys in the 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:
-
decrypt
-
encrypt
-
generate_data_key
-
generate_data_key_pair
-
generate_data_key_pair_without_plaintext
Eventual consistency: The KMS API follows an eventual consistency model. For more information, see KMS eventual consistency.
Usage¶
kms_generate_data_key_without_plaintext(KeyId, EncryptionContext,
KeySpec, NumberOfBytes, GrantTokens, DryRun)
Arguments¶
KeyId
[required] 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
describe_key
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
list_keys
ordescribe_key
. To get the alias name and alias ARN, uselist_aliases
.EncryptionContext
Specifies the encryption context that will be used when encrypting the data key.
Do not include confidential or sensitive information in this field. This field may be displayed in plaintext in CloudTrail logs and other output.
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 Key Management Service Developer Guide.
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.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.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 Key Management Service Developer Guide.
DryRun
Checks if your request will succeed.
DryRun
is an optional parameter.To learn more about how to use this parameter, see Testing your KMS API calls in the Key Management Service Developer Guide.
Value¶
A list with the following syntax:
Request syntax¶
svc$generate_data_key_without_plaintext(
KeyId = "string",
EncryptionContext = list(
"string"
),
KeySpec = "AES_256"|"AES_128",
NumberOfBytes = 123,
GrantTokens = list(
"string"
),
DryRun = TRUE|FALSE
)