How to Use the Command 'paperkey' (with Examples)

Paperkey is a tool crafted to handle OpenPGP keys, focusing primarily on the archival aspect of secret keys. OpenPGP keys are composed of both public and private components. While public keys are easy to back up and reproduce, secret keys are more sensitive and require thorough protection. Paperkey addresses this by breaking down the secret component of an OpenPGP key into printable text format and later helps in reconstructing the key using the public part and the saved secret data. This provides a secure way to store and retrieve private keys in case of data loss, maintaining your cryptographic security.

Use Case 1: Take a Specific Secret Key and Generate a Text File with the Secret Data

Code:

paperkey --secret-key path/to/secret_key.gpg --output path/to/secret_data.txt

Motivation:

In situations where you need to back up a sensitive OpenPGP secret key for secure storage, converting the key into a human-readable text format provides an effective solution. This form increases longevity and resilience against hardware failures, as it can be printed on paper physically and stored securely. If digital backups corrupt or degrade, the printout of the text file can be manually re-entered or scanned for reconstruction.

Explanation:

• --secret-key path/to/secret_key.gpg: This option specifies the location of the original secret key file. The path provided should point to the exact file containing the secret component of your OpenPGP key that you wish to back up.
• --output path/to/secret_data.txt: This argument defines the destination file where the parsed and printable secret data will be stored. By specifying a text file, you ensure that the secret data can be easily viewed and printed for physical archiving.

Example Output:

The command will yield a text file, secret_data.txt, containing the processed secret key information in a format that can easily be printed or transferred without losing the key’s integrity.

Use Case 2: Take the Secret Key Data in secret_data.txt and Combine it with the Public Key to Reconstruct the Secret Key

Code:

paperkey --pubring path/to/public_key.gpg --secrets path/to/secret_data.txt --output secret_key.gpg

Motivation:

Once a secret key has been archived successfully in a text format, it is vital to have a method to reconstruct the complete secret key when required. Combining the public key, which is often easier to store digitally, with the archived secret data allows the restoration of the fully functional secret key. This use case is critical for data recovery scenarios when restoring encrypted communications or previously encrypted files.

Explanation:

• --pubring path/to/public_key.gpg: This argument specifies the path to the public key ring file, which contains the public key counterpart of the secret key you wish to reconstruct. The public key is needed to provide all the non-sensitive data that is not included in secret_data.txt.
• --secrets path/to/secret_data.txt: Here, you provide the path to the text file containing the secret data extracted earlier with paperkey. This acts as the source of private information required to rebuild the key.
• --output secret_key.gpg: This option specifies the path to the output file that will store the reconstructed secret key, making it ready for import back into your OpenPGP key management utility.

Example Output:

Upon execution, a new file secret_key.gpg is created, restoring the full functionality of the secret key, which can now be imported and used as required in usual cryptographic applications.

Use Case 3: Export a Specific Secret Key and Generate a Text File with the Secret Data

Code:

gpg --export-secret-key key | paperkey --output path/to/secret_data.txt

Motivation:

Sometimes, direct access to the secret key file is not immediately possible, but making a backup remains essential. By exporting the secret key directly from your GPG setup using the gpg command in piped action with paperkey, users can achieve backup without extra intermediate files. This strategy is indispensable for swiftly transferring your secret key to a safeguarding format with minimal steps involved.

Explanation:

• gpg --export-secret-key key: This command portion uses GPG to identify and export the designated secret key. The key should be replaced by the actual key ID or email associated with the secret key you need to back up.
• |: The pipe (|) symbol is used in Unix-like shell environments to send data output from one command as input to another, creating a seamless flow from gpg to paperkey.
• paperkey --output path/to/secret_data.txt: As before, this paperkey command converts the secret key segment obtained from gpg into text format, directing it into secret_data.txt.

Example Output:

This process produces secret_data.txt, encapsulating your secret key’s critical private data, ready for safe archival or future restoration endeavors.

Conclusion:

Paperkey is a potent utility in the realm of cryptography, providing methods to ensure that the invaluable secret keys can be effectively backed up, stored, and restored. By following these use cases, users can safeguard their cryptographic assets efficiently against data loss, mitigating the risks often associated with digital-only storage solutions.