Unwrapping keys

IBM® Key Protect combines the strength of multiple algorithms to protect the privacy and the integrity of your encrypted data. You can unwrap a data encryption keyA cryptographic key used to encrypt data that is stored in an application. (DEK), to access its contents by using the IBM® Key Protect for IBM Cloud® API and Console. Unwrapping a DEK decrypts and checks the integrity of its contents, returning the original key material to your IBM Cloud data service.

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

Unwrapping a key using the console

If you already have an instance of Key Protect and you wish to encrypt your DEK by using a graphical interface, you can use the IBM Cloud console.

After you import or create your own keys, complete the following steps to wrap your data using the key:

Log in to the IBM Cloud console.
From the Menu, choose the Resource List to view a list of your resources.
From your IBM Cloud resource list, select your provisioned instance of Key Protect.
Choose the Root key that you used to originally wrap your data from the list of your keys.
Click the ⋯ icon to open a list of options for the DEK that you want to unwrap.
Click the Envelope encryption option to open the side panel. Choose the "Unwrap key" tab if it is not already highlighted.
Supply any required text for the above in the appropriate fields, including the ciphertext and any additional data you stored locally for the purpose of unwrapping the DEK.
Click Unwrap Key button.

Unwrapping keys by using the 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/<keyID_or_alias>/actions/unwrap

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

Retrieve your service and authentication credentials to work with keys in the service.
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 Key Protect instance by retrieving a list of your keys, or by accessing the Key Protect dashboard.
Copy the ciphertext value that was returned during the initial wrap request.

Run the following curl command to decrypt and authenticate the key material.

$ curl -X POST \
    "https://<region>.kms.cloud.ibm.com/api/v2/keys/<keyID_or_alias>/actions/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 "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 unwrap 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 is a part of. 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	Optional.The unique identifier that is used to track and correlate transactions.
additional_data	Optional.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 he 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 Key Protect 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

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

Download and install OpenSSL.
Decode your base64 encoded key material string by running the following command:
```
openssl base64 -d -in <infile> -out <outfile>
```

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

Table 2. 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.