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Recipe 7.12 Signing a Text File

7.12.1 Problem

You want to attach a digital signature to a text file to verify its authenticity, leaving the file human-readable.

7.12.2 Solution

$ gpg --clearsign myfile

You'll be prompted for your passphrase.

7.12.3 Discussion

If your original file has this content:

Hello world!

then the signed file will look something like this:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hello world!
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see http://www.gnupg.org

iD8DBQE9WFNU5U0ZSgD1tx8RAkAmAJ4wWTKWSy6C30raF2RWfQ6Eh8ZXAQCePUW3
N9JVeHSgYuSFu6XPLKW+2XU=
=5XaU
-----END PGP SIGNATURE-----

Anyone who has your public key can check the signature in this file using gpg, thereby confirming that the file is from you. [Recipe 7.15]

7.12.4 See Also

gpg(1).



    		Preface
    		Chapter 1. System Snapshots with Tripwire
    		Chapter 2. Firewalls with iptables and ipchains
    		Chapter 3. Network Access Control
    		Chapter 4. Authentication Techniques and Infrastructures
    		Chapter 5. Authorization Controls
    		Chapter 6. Protecting Outgoing Network Connections
    		Chapter 7. Protecting Files
    		Recipe 7.1 Using File Permissions
    		Recipe 7.2 Securing a Shared Directory
    		Recipe 7.3 Prohibiting Directory Listings
    		Recipe 7.4 Encrypting Files with a Password
    		Recipe 7.5 Decrypting Files
    		Recipe 7.6 Setting Up GnuPG for Public-Key Encryption
    		Recipe 7.7 Listing Your Keyring
    		Recipe 7.8 Setting a Default Key
    		Recipe 7.9 Sharing Public Keys
    		Recipe 7.10 Adding Keys to Your Keyring
    		Recipe 7.11 Encrypting Files for Others
    		Recipe 7.12 Signing a Text File
    		Recipe 7.13 Signing and Encrypting Files
    		Recipe 7.14 Creating a Detached Signature File
    		Recipe 7.15 Checking a Signature
    		Recipe 7.16 Printing Public Keys
    		Recipe 7.17 Backing Up a Private Key
    		Recipe 7.18 Encrypting Directories
    		Recipe 7.19 Adding Your Key to a Keyserver
    		Recipe 7.20 Uploading New Signatures to a Keyserver
    		Recipe 7.21 Obtaining Keys from a Keyserver
    		Recipe 7.22 Revoking a Key
    		Recipe 7.23 Maintaining Encrypted Files with Emacs
    		Recipe 7.24 Maintaining Encrypted Files with vim
    		Recipe 7.25 Encrypting Backups
    		Recipe 7.26 Using PGP Keys with GnuPG
    		Chapter 8. Protecting Email
    		Chapter 9. Testing and Monitoring
    		Colophon