“Pretty Good Privacy is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications”, Wikipedia. It basically operates in Linux, macOS, and Windows.
PGP Working System
PGP working system almost entirely based on keys. It uses public and private keys. You must know the public key of the person you want to send an encrypted message to. Your message would be signed by them with their public key for decrypting with their private key. You are not supposed to share or tell your private key to anyone. No one would be able to intercept your message because of End-to-end encryption.
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To handle the decryption and encryption process while using PGP you would require additional software. It happens in most email clients. The additional software could be FlowCrypt or Mailvelope. PGP can be used with a free or paid ProtonMail account. For this, you can initiate it to utilize for some email addresses and later just ignore it because ProtonMail already supports OpenPGP.
Tip: If you’re already sending an email to another ProtonMail user, then you don’t need to worry about this, since messages sent between ProtonMail addresses are already end-to-end encrypted anyway. This is only necessary if you want to exchange encrypted messages with people who aren’t using ProtonMail.
PGP is mainly for privacy concerns. If you want to share an encrypted message with anyone who is not using Proton Mail, you can enable PGP and ensure privacy. Exchange of emails between the users of Proton Mail does not require this as those messages are already end-to-end encrypted.
Sharing Public Key
The first step would be of course exchanging the keys with the person you are communicating with. For that follow these steps;
- Sign in to a ProtonMail account.
- To start writing a new email, click on the “Compose” button in the top-left corner of your screen.
- Enter the address of the user with whom you are trying to establish encrypted communication.
- Now click on the “More” drop-down icon.
- Check the “Attach Public Key”. It should be ticked.
- Add a message to your email body, it would notify the user that your public key is attached.
- Click on Settings, go to Security and enable “Automatically attach public key” under PGP Settings, in this way you can attach your public key to all outgoing mail.
Contact’s Public Key
The recipient would be using their PGP in their own way and they would send their public key which would be in the form of a file attachment.
- You will receive an email with a file attachment which is a public key.
- ProtonMail would ask you to trust it.
- Click on “Trust Key”.
- Check “Use For Encryption”, it would be ticked as it registers email address along with the public key.
- Click on the contact at the top of the page and create a new “Contacts” if the person has sent you the public key through some other means.
- Upload the file you’ve received by using the same email from which you received the key.
- Check “Use for Encryption”. it should be ticked.
- You can also manually upload a recipient’s public key using ProtonMail’s Contacts.
- Repeat the same process for other contacts.
Communication is now extremely secure with keys exchanged and also the address book is updated with the right keys. This process through which PGP is relatively the best encryption tool.