Rewrapping keys

Reencrypt your data encryption keys by using the IBM® Key Protect API.

When you rotate a root key in Key Protect, new cryptographic key material becomes available for protecting the data encryption keys (DEKs) that are associated with the root key. With the rewrap API, you can reencrypt or rewrap your DEKs without exposing the keys in their plaintext form.

To learn how envelope encryption helps you control the security of at rest data in the cloud, see Protecting data with envelope encryption.

Rewrapping keys by using the API

You can reencrypt a specified data encryption key (DEK) with a root key that you manage in Key Protect, without exposing the DEK in its plaintext form.

Rewrapping keys works by combining unwrap and wrap calls to the service. For example, you can emulate a rewrap operation by first calling the unwrap API to access a DEK, and then calling the wrap API to reencrypt the DEK by using the newest root key material.

After you rotate a root key in the service, rewrap a data encryption key that is associated with the root key by making a POST call to the following endpoint.

https://<region>.kms.cloud.ibm.com/api/v2/keys/<keyID_or_alias>/actions/rewrap

Retrieve your service and authentication credentials to work with keys in the service.
Copy the ID of the rotated root key that you used to perform the initial wrap request.

You can retrieve the ID for a key by making a GET api/v2/keys request, or by viewing your keys in the Key Protect GUI.
Copy the ciphertext value that was returned during the latest wrap request.

Rewrap the key with the latest root key material by running the following curl command.

$ curl -X POST \
    "https://<region>.kms.cloud.ibm.com/api/v2/keys/<keyID_or_alias>/actions/rewrap" \
    -H "accept: application/vnd.ibm.kms.key_action+json" \
    -H "authorization: Bearer <IAM_token>" \
    -H "bluemix-instance: <instance_ID>" \
    -H "content-type: application/vnd.ibm.kms.key_action+json" \
    -H "x-kms-key-ring: <key_ring_ID>" \
    -H "correlation-id: <correlation_ID>" \
    -d '{
            "ciphertext": "<encrypted_data_key>",
            "aad": [
                "<additional_data>",
                "<additional_data>"
            ]
        }'

Replace the variables in the example request according to the following table.

Table 1. Describes the variables that are needed to rewrap keys in Key Protect.
Variable	Description
region	Required. The region abbreviation, such as `us-south` or `eu-gb`, that represents the geographic area where your Key Protect instance resides. For more information, see Regional service endpoints.
keyID_or_alias	Required. The unique identifier or alias for the root key that you used for the initial wrap request.
IAM_token	Required. Your IBM Cloud access token. Include the full contents of the IAM token, including the Bearer value, in the curl request. For more information, see Retrieving an access token.
instance_ID	Required. The unique identifier that is assigned to your Key Protect service instance. For more information, see Retrieving an instance ID.
key_ring_ID	Optional. The unique identifier of the key ring that the key belongs to. If unspecified, Key Protect will search for the key in every key ring associated with the specified instance. It is recommended to specify the key ring ID for a more optimized request. Note: The key ring ID of keys that are created without an `x-kms-key-ring` header is: default. For more information, see Grouping keys.
correlation_ID	The unique identifier that is used to track and correlate transactions.
encrypted_data_key	Required. The ciphertext value that was returned by the original wrap operation.
additional_data	OptionalThe additional authentication data (AAD) that is used to further secure the key. Each string can hold up to 255 characters. If you supplied AAD for the initial wrap call, you must specify the same AAD during the subsequent unwrap or rewrap calls. Important: The Key Protect service does not save additional authentication data. If you supply AAD, save the data to a secure location to ensure that you can access and provide the same AAD during subsequent unwrap or rewrap requests.

The newly wrapped data encryption key, original key version (keyVersion) that is associated with the supplied ciphertext and latest key version ( rewrappedKeyVersion) associated with the new ciphertext is returned in the response entity-body. The following JSON object shows an example returned value.

{
    "ciphertext": "eyJjaX ... h0Ijoi ... c1ZCJ9",
    "keyVersion": {
        "id": "02fd6835-6001-4482-a892-13bd2085f75d"
    },
    "rewrappedKeyVersion": {
        "id": "12e8c9c2-a162-472d-b7d6-8b9a86b815a6"
    }
}

Store and use the new ciphertext value for future envelope encryption operations so that your data is protected by the latest root key.

Optional Validation

Verify that the key was successfully rewrapped by base64 decoding the ciphertext value.

$ echo <ciphertext> | base64 --decode

Replace <ciphertext> with the base64 encoded value that was returned in the previous step. The following JSON object shows an example CLI output.

{
    "ciphertext": "mIzRrwZAA8+WqRckG6gt1ji8HlEEJPSiV+TRBSR4GVr+FlAZlC5KvRriRF0=",
    "iv": "lbwxXlAW2DS7+5jGz5Y1Kg==",
    "version": "4.0.0",
    "handle": "8e309bae-b3ec-4270-9b87-89f8697fe54f"
}