unwrap-keys.md

copyright	lastupdated	keywords	subcollection
years 2017, 2020	2020-07-10	unwrap key, decrypt key, decrypt data encryption key, access data encryption key, envelope encryption API examples	key-protect

{:shortdesc: .shortdesc} {:screen: .screen} {:pre: .pre} {:table: .aria-labeledby="caption"} {:external: target="_blank" .external} {:codeblock: .codeblock} {:tip: .tip} {:note: .note} {:important: .important} {:term: .term}

Unwrapping keys

{: #unwrap-keys}

You can unwrap a data encryption key to access its contents by using the {{site.data.keyword.keymanagementservicefull}} API. Unwrapping a DEK decrypts and checks the integrity of its contents, returning the original key material to your {{site.data.keyword.cloud_notm}} data service. {: shortdesc}

To learn how key wrapping helps you control the security of at-rest data in the cloud, see Protecting data with envelope encryption. {: tip}

Unwrapping keys by using the API

{: #unwrap-key-api}

After you make a wrap call to the service, you can unwrap a specified data encryption key (DEK) to access its contents by making a POST call to the following endpoint.

https://<region>.kms.cloud.ibm.com/api/v2/keys/<key_id>?action=unwrap

{: codeblock}

Root keys that contain the same key material can unwrap the same data encryption key (WDEK). {: note}

1. Retrieve your service and authentication credentials to work with keys in the service.

2. Copy the ID of the root key that you used to perform the initial wrap request.

You can find the ID for a key in your service instance by retrieving a list of your keys, or by accessing the {{site.data.keyword.keymanagementserviceshort}} dashboard.

3. Copy the ciphertext value that was returned during the initial wrap request.

4. Run the following cURL command to decrypt and authenticate the key material.

   curl -X POST \
     'https://<region>.kms.cloud.ibm.com/api/v2/keys/<key_ID>?action=unwrap' \
     -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 'correlation-id: <correlation_ID>' \
     -d '{
       "ciphertext": "<encrypted_data_key>",
       "aad": [
         "<additional_data>",
         "<additional_data>"
       ]
     }'
   

   {: codeblock}

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

   Table 1. Describes the variables that are needed to unwrap keys in {{site.data.keyword.keymanagementserviceshort}}.

   Variable	Description
   region	Required. The region abbreviation, such as us-south or eu-gb, that represents the geographic area where your {{site.data.keyword.keymanagementserviceshort}} service instance resides. For more information, see [Regional service endpoints](/docs/key-protect?topic=key-protect-regions#service-endpoints).
   key_ID	Required. The unique identifier for the root key that you used for the initial wrap request.
   IAM_token	Required. Your {{site.data.keyword.cloud_notm}} 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](/docs/key-protect?topic=key-protect-retrieve-access-token).
   instance_ID	Required. The unique identifier that is assigned to your {{site.data.keyword.keymanagementserviceshort}} service instance. For more information, see [Retrieving an instance ID](/docs/key-protect?topic=key-protect-retrieve-instance-ID).
   correlation_ID	The unique identifier that is used to track and correlate transactions.
   additional_data	The additional authentication data (AAD) that is used to further secure the key. Each string can hold up to 255 characters. If you supply AAD when you make a wrap call to the service, you must specify the same AAD during the unwrap call.
   encrypted_data_key	Required. The ciphertext value that was returned during a wrap operation.

   The original key material is returned in the response entity-body. The response body also contains the ID of the key version that was used to unwrap the supplied ciphertext.

   The plaintext that is returned is base64 encoded. For more information on how to decode your key material, see Decoding your key material. The following JSON object shows an example returned value.

   {
     "plaintext": "Rm91ciBzY29yZSBhbmQgc2V2ZW4geWVhcnMgYWdv",
     "keyVersion": {
       "id": "02fd6835-6001-4482-a892-13bd2085f75d"
     }
   }

   If {{site.data.keyword.keymanagementserviceshort}} detects that you rotated the root key that is used to unwrap and access your data, the service also returns a newly wrapped data encryption key (ciphertext) in the unwrap response body. The latest key version (rewrappedKeyVersion) that is associated with the new ciphertext is also returned. Store and use the new ciphertext value for future envelope encryption operations so that your data is protected by the latest root key.

Decoding your key material

{: #how-to-decode-key-material}

When you unwrap a data encryption key, the key material is returned in base64 encoding. You will need to decode the key before encrypting it.

Using OpenSSL to decode key material

{: #open-ssl-encoding-root-unwrap}

1. Download and install OpenSSL{: external}.

2. Base64 encode your key material string by running the following command:

   $ openssl base64 -d -in <infile> -out <outfile>
   

   {: codeblock}

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

   Table 3. Describes the variables that are needed to decode your key material.

   Variable	Description
   infile	The name of the file where your base64 encoded key material string resides.
   outfile	The name of the file where your decoded key material will be be outputted once the command has ran.

If you want to output the decoded material in the command line directly rather than a file, run the command openssl enc -base64 -d <<< '<key_material_string>', where key_material_string is the returned plaintext from your unwrap request. {: note}