paws.security.identity (version 0.1.0)

kms_generate_data_key: Returns a data encryption key that you can use in your application to encrypt data locally

Description

Returns a data encryption key that you can use in your application to encrypt data locally.

Usage

kms_generate_data_key(KeyId, EncryptionContext, NumberOfBytes, KeySpec,
  GrantTokens)

Arguments

KeyId

[required] The identifier of the CMK under which to generate and encrypt the data encryption 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.

EncryptionContext

A set of key-value pairs that represents additional authenticated data.

For more information, see Encryption Context in the AWS Key Management Service Developer Guide.

NumberOfBytes

The length of the data encryption 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.

KeySpec

The length of the data encryption key. Use AES_128 to generate a 128-bit symmetric key, or AES_256 to generate a 256-bit symmetric key.

GrantTokens

A list of grant tokens.

For more information, see Grant Tokens in the AWS Key Management Service Developer Guide.

Request syntax

svc$generate_data_key(
  KeyId = "string",
  EncryptionContext = list(
    "string"
  ),
  NumberOfBytes = 123,
  KeySpec = "AES_256"|"AES_128",
  GrantTokens = list(
    "string"
  )
)

Details

You must specify the customer master key (CMK) under which to generate the data key. You must also specify the length of the data key using either the KeySpec or NumberOfBytes field. You must specify one field or the other, but not both. For common key lengths (128-bit and 256-bit symmetric keys), we recommend that you use KeySpec. To perform this operation on a CMK in a different AWS account, specify the key ARN or alias ARN in the value of the KeyId parameter.

This operation returns a plaintext copy of the data key in the Plaintext field of the response, and an encrypted copy of the data key in the CiphertextBlob field. The data key is encrypted under the CMK specified in the KeyId field of the request.

We recommend that you use the following pattern to encrypt data locally in your application:

1. Use this operation (GenerateDataKey) to get a data encryption key.

2. Use the plaintext data encryption key (returned in the Plaintext field of the response) to encrypt data locally, then erase the plaintext data key from memory.

3. Store the encrypted data key (returned in the CiphertextBlob field of the response) alongside the locally encrypted data.

To decrypt data locally:

1. Use the Decrypt operation to decrypt the encrypted data key into a plaintext copy of the data key.

2. Use the plaintext data key to decrypt data locally, then erase the plaintext data key from memory.

To return only an encrypted copy of the data key, use GenerateDataKeyWithoutPlaintext. To return a random byte string that is cryptographically secure, use GenerateRandom.

If you use the optional EncryptionContext field, you must store at least enough information to be able to reconstruct the full encryption context when you later send the ciphertext to the Decrypt operation. It is a good practice to choose an encryption context that you can reconstruct on the fly to better secure the ciphertext. For more information, see Encryption Context in the AWS Key Management Service Developer Guide.

The result of this operation varies with the key state of the CMK. For details, see How Key State Affects Use of a Customer Master Key in the AWS Key Management Service Developer Guide.

Examples

# NOT RUN {
# The following example generates a 256-bit symmetric data encryption key
# (data key) in two formats. One is the unencrypted (plainext) data key,
# and the other is the data key encrypted with the specified customer
# master key (CMK).
# }
# NOT RUN {
svc$generate_data_key(
  KeyId = "alias/ExampleAlias",
  KeySpec = "AES_256"
)
# }
# NOT RUN {
# }