Overview

I am not gonna debate on whether you should encrypt your communications or not. That’s your choice. Also this is not a tutorial on how PGP works or how does it encrypt your data. You can easily find these on web. One important thing I would like you to read is the difference between PGP and GPG. Let me highlight key differences below in case the web page is lost

  • PGP uses RSA and IDEA encryption algorithm whereas GPG uses NIST AES, Advanced Encryption Standard.
  • Phil Zimmermann (Developer) wrote PGP. Symantec aquired PGP corp and hence Symantec owns PGP currently. Read more on it here. GPG (developed by Werner Koch) is still free to use, free to distribute and free to modify. GPG can open and unencrypt any PGP and OpenPGP standards file.
  • PGP stands for Pretty Good Privacy whereas GPG stands for Gnu Privacy Guard.

My post is a really simple cheatsheet for command line gpg which you can use for quick reference. Forgive me if i have missed out on anything. Better to mention in comments so that I update this post. Thanks!

Using gpg

  • Generate Key

      gpg --gen-key
    

    When it asks “What keysize do you want? (2048)”, just type 4096. You can just go with the defaults for other values. One thing I wanna tell is that if it tells you that there isn’t enough entropy, you should open a new terminal and type ls -R /. Let it execute and side by side you can do lot of I/O and utilize disk. That should be enough for gpg.

  • List keys - Lists all the public keys

      gpg --list-keys
    
  • List Private Keys - Lists all the private keys

      gpg --list-secret-keys
    
  • Editing your key - Hepls in editing key

      gpg --edit-key yourEmailId
    
  • Adding multiple usernames - Add new real name(username) to key

      gpg --edit-key yourEmailId
    

    Now you have entered the GPG shell

      Command> adduid
      Command> save
    
  • Set Primary uid - Sets primary uid if multiple uids are in one key. Do as above to go to gpg shell.

      Command> uid 1
      Command> primary
      Command> save
    
  • Adding key to keyserver - Upload/submit your public key to a keyserver

      gpg --keyserver subkeys.pgp.net --send-keys *keyID*
    
  • Get key from Keyserver - Fetch anyone’s public key from keyserver

      gpg --keyserver subkeys.pgp.net --recv-keys *authorKeyID*
    
  • Generating Fingerprint - Generates a fingerprint (Less characters for easy verification)

      gpg --fingerprint > fingerprint
    
  • Import Public Key - Attach someone’s public key to your keyring

      gpg --import somepubkeyfile
    

    This adds the public key in somepubkeyfile to your public key ring.

  • Export Keys - Export/Dump public and private keys to files

      gpg --export -a "Real Name that you entered" > public
    
      gpg --export-secret-key -a "Real Name that you entered" > private
    
  • Encrypting some file - Lets you encrypt some data

      gpg -e -u "Real Name that you enetered" -r "Reciever Real Name" example.tar.gz
    

    -u option to specify which private key you want to use -r option to specify which public key you want to use (You must have that public key first) example.tar.gz is the file I want to encrypt. It will generate example.tar.gz.gpg file which is the only file you need to send to the reciever.

  • Decrypting some file - Lets you decrypt data

      gpg -d example.tar.gz.gpg > example.tar.gz
    

It will automatically choose your secret key and will prompt you for your password. It generates a example.tar.gz file.

  • Delete Key Pair - Deletes your public and associated secret key

      gpg --delete-secret-and-public-keys "Real Name that you entered"
    
  • Revocation Certificate - Generates revocation certification

      gpg --gen-revoke
    

    It creates a revocation certificate which means that when you will distribute this revocation certificate to keyserver, it will know that your respective key is no longer a valid key. This can also be achieved using

      gpg --edit-key "Real Name You entered"
    

    The uid will be marked with *. For that uid, you can revoke using Command> revuid

    and then finally update your key on keyserver using

      gpg --keyserver subkeys.pgp.net --send-keys *keyID*
    


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