GNU Privacy Guard (GPG, also called ) is a free encryption software you can use to encrypt and decrypt files. While the for GnuPG is excellent, this is a quick cheatsheet on how to get started with GPG. GnuPG documentation Install GPG Mac You need homebrew to be able to install gpg on Mac . If you don’t have homebrew installed, you can learn how to do that . After that, it is a one line command. here brew install gnupg Windows There are many ways to install gpg on windows. Perhaps the easiest way to is to go to and use the simple installer for the current GnuPG. GnuPG site Red Hat / CentOS yum install gnupg Ubuntu / Debian If you are using these Linux distributions, you might want to change the commands in this tutorial to after using the command below. You can find more infomation on this . gpg2 here sudo apt-get install gnupg2 Entire Process GPG uses a method of encryption known as public key (asymmetric) , which provides a number of advantages and benefits. In a public key (asymmetric) encryption system, any person can encrypt a message using a public key. That encrypted message can only be decrypted with the corresponding private key. This section just goes through the GPG commands to do this. If you don’t understand asymmetric encryption, there is a wonderful youtube video on it . cryptography here Generating Key Pair (Private and Public Keys) Create your keys. This will generate a key pair. One is a private key which you need to keep safe and a public key which you can share with other people. gpg --gen-key Enter name, email address, and O You will have to enter a password. Keep it somewhere safe. Enter and re-enter your password Export your public key. In this case, is the name of my public key. It will be whatever you named your key in step 1. richter gpg --export --armor richter > richterPublicKey.asc Export your public key Send the public key you exported to another person. Public Key Holder Import another persons public key. You need to substitute for the public key you wish to import. richterPublicKey gpg --import richterPublicKey.asc import other person’s key Trust the public key. This will prevent GPG from warning you every time you encrypt something with that public key. You need to substitute with the name of your public key. richter gpg --edit-key richter Enter trust Enter , , and then 5 y quit This step shows how to encrypt a file (in this case, I encrypted a file superSecret.txt). gpg --encrypt --recipient richter superSecret.txt Transfer the encrypted file to the private key holder. Private Key Holder After receiving the file, you can decrypt the file. You will have to enter your password. gpg --output superSecret.txt --decrypt superSecret.txt.gpg Keep in mind that you can also decrypt multiple files using the following command. gpg --decrypt-files *.gpg List Keys in your Keyring Public Keys You can view a list of public keys in your keyring as well as the name and email address associated with each key gpg --list-keys Private Keys The following command will list the private keys in your keyring. This will show the private keys you have (including the one you created or imported earlier) gpg --list-secret-keys Delete Keys from Keyring You can also delete keys from your keyring. Remove Public Key gpg --delete-key "User Name" Note that if you try to delete a public key when you have its associated private key you will run into an error. Remove Private Key gpg --delete-secret-key "User Name" How to Export and Import a Secret Key Export a Secret Key You can also export your secret key. gpg --export-secret-keys richter > privateKey.asc Import Secret Key gpg --import privateKey.asc Not done yet, you still need to ultimately trust a key. You will need to make sure that you also ultimately trust a key. gpg --edit-key orysya enter trust Enter , , and then 5 y quit You can check this by using the command gpg --list-secret-keysgpg --list-keys Keep in mind that you could also . automate the trusting process expect -c "spawn gpg --edit-key {KEY} trust quit; send \"5\ry\r\"; expect eof" Conclusion I hope you find this tutorial useful. If you any questions or thoughts on the tutorial, feel free to reach out in the comments below or through . Twitter

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Public-key (asymmetric) Cryptography using GPG

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Public-key (asymmetric) Cryptography using GPG

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Michael Galarnyk

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