<a id="cli-aws-kms-generate-data-key"></a>

# generate-data-key

## Description

Returns a unique symmetric data key for use outside of KMS. This operation returns a plaintext copy of the data key and a copy that is encrypted under a symmetric encryption KMS key that you specify. The bytes in the plaintext key are random; they are not related to the caller or the KMS key. You can use the plaintext key to encrypt your data outside of KMS and store the encrypted data key with the encrypted data.

To generate a data key, specify the symmetric encryption KMS key that will be used to encrypt the data key. You cannot use an asymmetric KMS key to encrypt data keys. To get the type of your KMS key, use the  DescribeKey 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 a 128-bit SM4 data key (China Regions only), specify a `KeySpec` value of `AES_128` or a `NumberOfBytes` value of `16` . The symmetric encryption key used in China Regions to encrypt your data key is an SM4 encryption key.

To get only an encrypted copy of the data key, use  GenerateDataKeyWithoutPlaintext . To generate an asymmetric data key pair, use the  GenerateDataKeyPair or  GenerateDataKeyPairWithoutPlaintext operation. To get a cryptographically secure random byte string, use  GenerateRandom .

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](https://docs.aws.amazon.com/kms/latest/developerguide/encrypt_context.html) in the *Key Management Service Developer Guide* .

> `GenerateDataKey` also supports [Amazon Web Services Nitro Enclaves](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/nitro-enclave.html) , which provide an isolated compute environment in Amazon EC2. To call `GenerateDataKey` for an Amazon Web Services Nitro enclave or NitroTPM, use the [Amazon Web Services Nitro Enclaves SDK](https://docs.aws.amazon.com/enclaves/latest/user/developing-applications.html#sdk) or any Amazon Web Services SDK. Use the `Recipient` parameter to provide the attestation document for the attested environment. `GenerateDataKey` returns a copy of the data key encrypted under the specified KMS key, as usual. But instead of a plaintext copy of the data key, the response includes a copy of the data key encrypted under the public key from the attestation document (`CiphertextForRecipient` ). For information about the interaction between KMS and Amazon Web Services Nitro Enclaves or Amazon Web Services NitroTPM, see [Cryptographic attestation support in KMS](https://docs.aws.amazon.com/kms/latest/developerguide/cryptographic-attestation.html) 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](https://docs.aws.amazon.com/kms/latest/developerguide/key-state.html) in the *Key Management Service Developer Guide* .

> **How to use your data key**

We recommend that you use the following pattern to encrypt data locally in your application. You can write your own code or use a client-side encryption library, such as the [Amazon Web Services Encryption SDK](https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/) , the [Amazon DynamoDB Encryption Client](https://docs.aws.amazon.com/dynamodb-encryption-client/latest/devguide/) , or [Amazon S3 client-side encryption](https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingClientSideEncryption.html) to do these tasks for you.

To encrypt data outside of KMS:

* Use the `GenerateDataKey` operation to get a data key.
* Use the plaintext data key (in the `Plaintext` field of the response) to encrypt your data outside of KMS. Then erase the plaintext data key from memory.
* Store the encrypted data key (in the `CiphertextBlob` field of the response) with the encrypted data.

To decrypt data outside of KMS:

* Use the  Decrypt operation to decrypt the encrypted data key. The operation returns a plaintext copy of the data key.
* Use the plaintext data key to decrypt data outside of KMS, then erase the plaintext data key from memory.

> **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:GenerateDataKey](https://docs.aws.amazon.com/kms/latest/developerguide/kms-api-permissions-reference.html) (key policy)

> **Related operations:**
* Decrypt
* Encrypt
* GenerateDataKeyPair
* GenerateDataKeyPairWithoutPlaintext
* GenerateDataKeyWithoutPlaintext

> **Eventual consistency** : The KMS API follows an eventual consistency model. For more information, see [KMS eventual consistency](https://docs.aws.amazon.com/kms/latest/developerguide/accessing-kms.html#programming-eventual-consistency) .

See also: [AWS API Documentation](https://docs.aws.amazon.com/goto/WebAPI/kms-2014-11-01/GenerateDataKey)

## Synopsis

```
  generate-data-key
--key-id <value>
[--encryption-context <value>]
[--number-of-bytes <value>]
[--key-spec <value>]
[--grant-tokens <value>]
[--recipient <value>]
[--dry-run | --no-dry-run]
[--cli-input-json | --cli-input-yaml]
[--generate-cli-skeleton <value>]
[--debug]
[--endpoint-url <value>]
[--no-verify-ssl]
[--no-paginate]
[--output <value>]
[--query <value>]
[--profile <value>]
[--region <value>]
[--version <value>]
[--color <value>]
[--no-sign-request]
[--ca-bundle <value>]
[--cli-read-timeout <value>]
[--cli-connect-timeout <value>]
[--cli-binary-format <value>]
[--no-cli-pager]
[--cli-auto-prompt]
[--no-cli-auto-prompt]
[--cli-error-format <value>]
[--help]
```

## Options

`--key-id` (string) [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  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 .

> Constraints:

> * min: `1`
> * max: `2048`

`--encryption-context` (map)

> Specifies the encryption context that will be used when encrypting the data key.

> #### WARNING
> 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](https://docs.aws.amazon.com/kms/latest/developerguide/encrypt_context.html) in the *Key Management Service Developer Guide* .

> key -> (string)

> value -> (string)

Shorthand Syntax:

```
KeyName1=string,KeyName2=string
```

JSON Syntax:

```json
{"string": "string"
  ...}
```

`--number-of-bytes` (integer)

> Specifies 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 128-bit (16-byte) and 256-bit (32-byte) data keys, use the `KeySpec` parameter.

> You must specify either the `KeySpec` or the `NumberOfBytes` parameter (but not both) in every `GenerateDataKey` request.

> Constraints:

> * min: `1`
> * max: `1024`

`--key-spec` (string)

> Specifies the length of the data key. Use `AES_128` to generate a 128-bit symmetric key, or `AES_256` to generate a 256-bit symmetric key.

> You must specify either the `KeySpec` or the `NumberOfBytes` parameter (but not both) in every `GenerateDataKey` request.

> Possible values:

> * `AES_256`
> * `AES_128`

`--grant-tokens` (list)

> 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](https://docs.aws.amazon.com/kms/latest/developerguide/grants.html#grant_token) and [Using a grant token](https://docs.aws.amazon.com/kms/latest/developerguide/using-grant-token.html) in the *Key Management Service Developer Guide* .

> Constraints:

> * min: `0`
> * max: `10`

> (string)

> > Constraints:

> > * min: `1`
> > * max: `8192`

Syntax:

```
"string" "string" ...
```

`--recipient` (structure)

> A signed [attestation document](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/nitro-enclave-how.html#term-attestdoc) from an Amazon Web Services Nitro enclave or NitroTPM, and the encryption algorithm to use with the public key in the attestation document. The only valid encryption algorithm is `RSAES_OAEP_SHA_256` .

> This parameter supports the [Amazon Web Services Nitro Enclaves SDK](https://docs.aws.amazon.com/enclaves/latest/user/developing-applications.html#sdk) or any Amazon Web Services SDK for Amazon Web Services Nitro Enclaves. It supports any Amazon Web Services SDK for Amazon Web Services NitroTPM.

> When you use this parameter, instead of returning the plaintext data key, KMS encrypts the plaintext data key under the public key in the attestation document, and returns the resulting ciphertext in the `CiphertextForRecipient` field in the response. This ciphertext can be decrypted only with the private key in the enclave. The `CiphertextBlob` field in the response contains a copy of the data key encrypted under the KMS key specified by the `KeyId` parameter. The `Plaintext` field in the response is null or empty.

> For information about the interaction between KMS and Amazon Web Services Nitro Enclaves or Amazon Web Services NitroTPM, see [Cryptographic attestation support in KMS](https://docs.aws.amazon.com/kms/latest/developerguide/cryptographic-attestation.html) in the *Key Management Service Developer Guide* .

> KeyEncryptionAlgorithm -> (string)

> > The encryption algorithm that KMS should use with the public key for an Amazon Web Services Nitro Enclave or NitroTPM to encrypt plaintext values for the response. The only valid value is `RSAES_OAEP_SHA_256` .

> > Possible values:

> > * `RSAES_OAEP_SHA_256`

> AttestationDocument -> (blob)

> > The attestation document for an Amazon Web Services Nitro Enclave or a NitroTPM. This document includes the enclave’s public key.

> > Constraints:

> > * min: `1`
> > * max: `262144`

Shorthand Syntax:

```
KeyEncryptionAlgorithm=string,AttestationDocument=blob
```

JSON Syntax:

```json
{
  "KeyEncryptionAlgorithm": "RSAES_OAEP_SHA_256",
  "AttestationDocument": blob
}
```

`--dry-run` | `--no-dry-run` (boolean)

> Checks if your request will succeed. `DryRun` is an optional parameter.

> To learn more about how to use this parameter, see [Testing your permissions](https://docs.aws.amazon.com/kms/latest/developerguide/testing-permissions.html) in the *Key Management Service Developer Guide* .

`--cli-input-json` | `--cli-input-yaml` (string)
Reads arguments from the JSON string provided. The JSON string follows the format provided by `--generate-cli-skeleton`. If other arguments are provided on the command line, those values will override the JSON-provided values. It is not possible to pass arbitrary binary values using a JSON-provided value as the string will be taken literally. This may not be specified along with `--cli-input-yaml`.

`--generate-cli-skeleton` (string)
Prints a JSON skeleton to standard output without sending an API request. If provided with no value or the value `input`, prints a sample input JSON that can be used as an argument for `--cli-input-json`. Similarly, if provided `yaml-input` it will print a sample input YAML that can be used with `--cli-input-yaml`. If provided with the value `output`, it validates the command inputs and returns a sample output JSON for that command. The generated JSON skeleton is not stable between versions of the AWS CLI and there are no backwards compatibility guarantees in the JSON skeleton generated.

## Global Options

`--debug` (boolean)

Turn on debug logging.

`--endpoint-url` (string)

Override command’s default URL with the given URL.

`--no-verify-ssl` (boolean)

By default, the AWS CLI uses SSL when communicating with AWS services. For each SSL connection, the AWS CLI will verify SSL certificates. This option overrides the default behavior of verifying SSL certificates.

`--no-paginate` (boolean)

Disable automatic pagination. If automatic pagination is disabled, the AWS CLI will only make one call, for the first page of results.

`--output` (string)

The formatting style for command output.

* json
* text
* table
* yaml
* yaml-stream
* off

`--query` (string)

A JMESPath query to use in filtering the response data.

`--profile` (string)

Use a specific profile from your credential file.

`--region` (string)

The region to use. Overrides config/env settings.

`--version` (string)

Display the version of this tool.

`--color` (string)

Turn on/off color output.

* on
* off
* auto

`--no-sign-request` (boolean)

Do not sign requests. Credentials will not be loaded if this argument is provided.

`--ca-bundle` (string)

The CA certificate bundle to use when verifying SSL certificates. Overrides config/env settings.

`--cli-read-timeout` (int)

The maximum socket read time in seconds. If the value is set to 0, the socket read will be blocking and not timeout. The default value is 60 seconds.

`--cli-connect-timeout` (int)

The maximum socket connect time in seconds. If the value is set to 0, the socket connect will be blocking and not timeout. The default value is 60 seconds.

`--cli-binary-format` (string)

The formatting style to be used for binary blobs. The default format is base64. The base64 format expects binary blobs to be provided as a base64 encoded string. The raw-in-base64-out format preserves compatibility with AWS CLI V1 behavior and binary values must be passed literally. When providing contents from a file that map to a binary blob `fileb://` will always be treated as binary and use the file contents directly regardless of the `cli-binary-format` setting. When using `file://` the file contents will need to properly formatted for the configured `cli-binary-format`.

* base64
* raw-in-base64-out

`--no-cli-pager` (boolean)

Disable cli pager for output.

`--cli-auto-prompt` (boolean)

Automatically prompt for CLI input parameters.

`--no-cli-auto-prompt` (boolean)

Disable automatically prompt for CLI input parameters.

`--cli-error-format` (string)

The formatting style for error output. By default, errors are displayed in enhanced format.

* legacy
* json
* yaml
* text
* table
* enhanced

`--help` (boolean)

Display help for the command/subcommand.

## Examples

#### NOTE
To use the following examples, you must have the AWS CLI installed and configured. See the [Getting started guide](https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html) in the *AWS CLI User Guide* for more information.

Unless otherwise stated, all examples have unix-like quotation rules. These examples will need to be adapted to your terminal’s quoting rules. See [Using quotation marks with strings](https://docs.aws.amazon.com/cli/latest/userguide/cli-usage-parameters-quoting-strings.html) in the *AWS CLI User Guide* .

**Example 1: To generate a 256-bit symmetric data key**

The following `generate-data-key` example requests a 256-bit symmetric data key for use outside of AWS. The command returns a plaintext data key for immediate use and deletion, and a copy of that data key encrypted under the specified KMS key. You can safely store the encrypted data key with the encrypted data.

To request a 256-bit data key, use the `key-spec` parameter with a value of `AES_256`. To request a 128-bit data key, use the `key-spec` parameter with a value of `AES_128`. For all other data key lengths, use the `number-of-bytes` parameter.

The KMS key you specify must be a symmetric encryption KMS key, that is, a KMS key with a key spec value of SYMMETRIC_DEFAULT.

```bash
aws kms generate-data-key \
    --key-id alias/ExampleAlias \
    --key-spec AES_256
```

Output:

```json
{
    "Plaintext": "VdzKNHGzUAzJeRBVY+uUmofUGGiDzyB3+i9fVkh3piw=",
    "KeyId": "arn:aws:kms:us-west-2:123456789012:key/a1b2c3d4-5678-90ab-cdef-EXAMPLE11111",
    "KeyMaterialId": "0b7fd7ddbac6eef27907413567cad8c810e2883dc8a7534067a82ee1142fc1e6",
    "CiphertextBlob": "AQEDAHjRYf5WytIc0C857tFSnBaPn2F8DgfmThbJlGfR8P3WlwAAAH4wfAYJKoZIhvcNAQcGoG8wbQIBADBoBgkqhkiG9w0BBwEwHgYJYIZIAWUDBAEuMBEEDEFogLqPWZconQhwHAIBEIA7d9AC7GeJJM34njQvg4Wf1d5sw0NIo1MrBqZa+YdhV8MrkBQPeac0ReRVNDt9qleAt+SHgIRF8P0H+7U="
}
```

The `Plaintext` (plaintext data key) and the `CiphertextBlob` (encrypted data key) are returned in base64-encoded format.

For more information, see [Data keys](https://docs.aws.amazon.com/kms/latest/developerguide/data-keys.html) in the *AWS Key Management Service Developer Guide*.
**Example 2: To generate a 512-bit symmetric data key**

The following `generate-data-key` example requests a 512-bit symmetric data key for encryption and decryption. The command returns a plaintext data key for immediate use and deletion, and a copy of that data key encrypted under the specified KMS key. You can safely store the encrypted data key with the encrypted data.

To request a key length other than 128 or 256 bits, use the `number-of-bytes` parameter. To request a 512-bit data key, the following example uses the `number-of-bytes` parameter with a value of 64 (bytes).

The KMS key you specify must be a symmetric encryption KMS key, that is, a KMS key with a key spec value of SYMMETRIC_DEFAULT.

NOTE: The values in the output of this example are truncated for display.

```bash
aws kms generate-data-key \
    --key-id a1b2c3d4-5678-90ab-cdef-EXAMPLE11111 \
    --number-of-bytes 64
```

Output:

```json
{
    "CiphertextBlob": "AQIBAHi6LtupRpdKl2aJTzkK6FbhOtQkMlQJJH3PdtHvS/y+hAEnX/QQNmMwDfg2korNMEc8AAACaDCCAmQGCSqGSIb3DQEHBqCCAlUwggJRAgEAMIICSgYJKoZ...",
    "Plaintext": "ty8Lr0Bk6OF07M2BWt6qbFdNB+G00ZLtf5MSEb4al3R2UKWGOp06njAwy2n72VRm2m7z/Pm9Wpbvttz6a4lSo9hgPvKhZ5y6RTm4OovEXiVfBveyX3DQxDzRSwbKDPk/...",
    "KeyId": "arn:aws:kms:us-west-2:123456789012:key/a1b2c3d4-5678-90ab-cdef-EXAMPLE11111",
    "KeyMaterialId": "0b7fd7ddbac6eef27907413567cad8c810e2883dc8a7534067a82ee1142fc1e6"
}
```

The `Plaintext` (plaintext data key) and `CiphertextBlob` (encrypted data key) are returned in base64-encoded format.

For more information, see [Data keys](https://docs.aws.amazon.com/kms/latest/developerguide/data-keys.html) in the *AWS Key Management Service Developer Guide*.

## Output

CiphertextBlob -> (blob)

> The encrypted copy of the data key. When you use the HTTP API or the Amazon Web Services CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded.

> Constraints:

> * min: `1`
> * max: `6144`

Plaintext -> (blob)

> The plaintext data key. When you use the HTTP API or the Amazon Web Services CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded. Use this data key to encrypt your data outside of KMS. Then, remove it from memory as soon as possible.

> If the response includes the `CiphertextForRecipient` field, the `Plaintext` field is null or empty.

> Constraints:

> * min: `1`
> * max: `4096`

KeyId -> (string)

> The Amazon Resource Name ([key ARN](https://docs.aws.amazon.com/kms/latest/developerguide/concepts.html#key-id-key-ARN) ) of the KMS key that encrypted the data key.

> Constraints:

> * min: `1`
> * max: `2048`

CiphertextForRecipient -> (blob)

> The plaintext data key encrypted with the public key from the attestation document. This ciphertext can be decrypted only by using a private key from the attested environment.

> This field is included in the response only when the `Recipient` parameter in the request includes a valid attestation document from an Amazon Web Services Nitro enclave or NitroTPM. For information about the interaction between KMS and Amazon Web Services Nitro Enclaves or Amazon Web Services NitroTPM, see [Cryptographic attestation support in KMS](https://docs.aws.amazon.com/kms/latest/developerguide/cryptographic-attestation.html) in the *Key Management Service Developer Guide* .

> Constraints:

> * min: `1`
> * max: `6144`

KeyMaterialId -> (string)

> The identifier of the key material used to encrypt the data key. This field is omitted if the request includes the `Recipient` parameter.

> Constraints:

> * min: `64`
> * max: `64`
> * pattern: `^[a-f0-9]+$`