GnuPG Tutorial — a really fun stuff

img credit > https://en.wikipedia.org/wiki/GNU_Privacy_Guard

Document Objective

• GnuPG implementation in details
• Fun with encryption in security/ privacy
• Integrate-able with BlockChain

Importing key

gpg --import <keyfile>

Generating key

gpg --gen-key
gpg --default-new-key-algo rsa4096 --gen-key

Generating a revocation key

gpg --gen-revoke --armor --output 20180717_revoke.asc <key_id>

Exporting key

• Exporting a public key

gpg --output exported.gpg --export my@email.org 
gpg --armor --export my@email.org 
gpg --armor --export --outfile file.asc <key_id>

• Exporting a private key

gpg --armor --export-private-keys <key_id>

Editing key (trusting key)

gpg --edit-key my@email.org
gpg> trust

Check https://www.gnupg.org/gph/en/manual/x334.html to trust and validate keys

Listing key(s)

gpg -k  # --list-public-keys
gpg --list-keys <name>

List secret keys

gpg --list-secret-keys --with-colon

Fingerprint

gpg --fingerprint my@email.org

Encrypting

• Sending encrypted message to a specific recipient

gpg -e -r <recipient_name> <file> 
gpg --output doc.gpg --encrypt --recipient my@mail.org  
gpg --encrypt --sign --armor -r recipient@email -r my@mail filename

• Encrypt with a symmetric cipher without using a public key

gpg --output doc.gpg --symmetric doc

Decrypting

gpg --output doc --decrypt doc.gpg

Signing public key

• Sign

gpg --sign-key <uid> 
gpg --output doc.sig --sign doc

• Verify signature

gpg --output doc --decrypt doc.sig

• Clearsigned doc, to sign usenet post or email msg

gpg --clearsign doc

~/.gnupg/gpg.conf

• cat ~/.gnupg/gpg.conf

default-key ABCDEFAB12345678 cipher-algo AES256

Uploading key to public key server

gpg --keyserver hkp://keyring.debian.org --send-key <key_id>
gpg --keyserver hkp://pool.sks-keyservers.net --send-key <key_id>

Cipher

3DES, Blowfish, and IDEA all use 128-bit keys, which means there are `$2^{128}$` possible keys. DES has `$2^{56}$` possible keys, which is lack of security for current computing power.

Backup your keys

umask 077; tar -cf $HOME/gnupg-backup.tar -C $HOME .gnupg

Working with Git

gpg --list-secret-keys --keyid-format LONG
git config --global user.signingkey <key_id>
echo 'export GPG_TTY=$(tty)' >> ~/.bashrc

References

https://www.gnupg.org/gph/en/manual/book1.html

https://www.digitalocean.com/community/tutorials/how-to-use-gpg-to-encrypt-and-sign-messages

http://www.queen.clara.net/pgp/art4.html

https://wiki.debian.org/Subkeys?action=show&redirect=subkeys

https://www.laurencegellert.com/2011/04/gnupg-howto-tutorial-notes/

https://help.github.com/articles/telling-git-about-your-gpg-key/

https://www.futureboy.us/pgp.html