OpenKeyChain on Cebulka Blog

PGP compendium - Encryption and popular PGP tools use guides (2024)

Sat, 17 Aug 2024 12:07:00 +0000

A collection of guides for the popular PGP tools: GPG4USB (Linux & Windows), GPA (Linux), Kleopatra (Linux & Windows), GPGSuite (macOS), OpenKeyChain (Android) and PGPro (iOS).

What is PGP / OpenPGP #

GnuPG (GPG, GNU Privacy Guard) is an open-source encryption software for secure End-to-End communication between two parties. It enables users to communicate securely by providing tools to encrypt and decrypt messages using the OpenPGP (Open Pretty Good Privacy) non-proprietary standard.

OpenPGP uses public key cryptography. To use OpenPGP, you must first generate a pair — public and private keys using GPG software. You can then share your public key with others, keeping your private key secret. Anyone who has the public key can use it to encrypt and verify information that only the holder of the private key can decrypt and sign.

Installation and configuration #

The basic GPG program runs from the command line but there are various front-ends such as GPG4USB, graphical interfaces for different operating systems. The portable GPG4USB program is cross-platform and easy to use but is no longer developed and has an outdated version of GPG. The GNU Privacy Assistant (GPA) tool is available on the Whonix-Workstation system. The Tails system as of version 5.0 has the Kleopatra tool, also known from the Gpg4win package for Windows systems.

Installation of GPG4USB (Linux & Windows)
Installation of GNU Privacy Assistant (Linux)
Installation of Kleopatra (Linux)
Installation of Kleopatra (Windows)
Installation of GPG Suite (macOS)
Installation of OpenKeychain (Android)
Installation of PGPro (iOS)

Key generation #

The user generates a pair of keys, a public key and a private key. The public key is shared with others, while the private key is kept secret. Private key is stored in GPG program files, so it is recommended to encrypt the operating system.

Key generation in GPG4USB (Linux & Windows)
Key generation in GNU Privacy Assistant (Linux)
Key generation in Kleopatra (Linux)
Key generation in Kleopatra (Windows)
Key generation in GPG Suite (macOS)
Key generation in OpenKeychain (Android)
Key generation in PGPro (iOS)

Private key backup #

A backup copy of the private key should be encrypted with VeraCrypt or TrueCrypt and placed on external media for protection against data loss.

Private key backup in GPG4USB (Linux & Windows)
Private key backup in GNU Privacy Assistant (Linux)
Private key backup in Kleopatra (Linux)
Private key backup in Kleopatra (Windows)
Private key backup in GPG Suite (macOS)
Private key backup in OpenKeychain (Android)
Private key backup in PGPro (iOS)

Importing public keys #

Import public keys of other users for encrypting messages and verifying digital signatures.

Importing public keys in GPG4USB (Linux & Windows)
Importing public keys in GNU Privacy Assistant (Linux)
Importing public keys in Kleopatra (Linux)
Importing public keys in Kleopatra (Windows)
Importing public keys inGPG Suite (macOS)
Importing public keys in OpenKeychain (Android)
Importing public keys in PGPro (iOS)

Message encryption #

The sender uses the recipient’s public key to encrypt the message. This ensures that only the intended recipient can decrypt it.

Message encryption in GPG4USB (Linux & Windows)
Message encryption in GNU Privacy Assistant (Linux)
Message encryption in Kleopatra (Linux)
Message encryption in Kleopatra (Windows)
Message encryption in GPG Suite (macOS)
Message encryption in OpenKeychain (Android)
Message encryption in PGPro (iOS)

Message decryption #

The recipient uses his private key to decrypt the encrypted message. By quoting a sufficient part of it in the reply, also confirms that has access to the private key.

Message decryption in GPG4USB (Linux & Windows)
Message decryption in GNU Privacy Assistant (Linux)
Message decryption in Kleopatra (Linux)
Message decryption in Kleopatra (Windows)
Message decryption in GPG Suite (macOS)
Message decryption in OpenKeychain (Android)
Message decryption in PGPro (iOS)

Signing messages #

The sender can use his private key to digitally sign the message. The signature acts as proof that the message was written by the key owner.

Signing messages in GPG4USB (Linux & Windows)
Signing messages in GNU Privacy Assistant (Linux)
Signing messages in Kleopatra (Linux)
Signing messages in Kleopatra (Windows)
Signing messages in GPG Suite (macOS)
Signing messages in OpenKeychain (Android)
Signing messages in PGPro (iOS)

Verifying messages #

After receiving a signed message, the recipient can use the sender’s public key to verify the digital signature of the message. A valid signature proves that the message was sent by the sender and has not been altered. The slightest change in the original message, even by one character, will cause the verification process to fail.

Verifying messages in GPG4USB (Linux & Windows)
Verifying messages in GNU Privacy Assistant (Linux)
Verifying messages in Kleopatra (Linux)
Verifying messages in Kleopatra (Windows)
Verifying messages in GPG Suite (macOS)
Verifying messages in OpenKeychain (Android)
Verifying messages in PGPro (iOS)

Troubleshooting

GnuPG version update in GPG4USB

OpenKeyChain for Android installation and operation guide

Sat, 17 Aug 2024 12:05:00 +0000

OpenKeyChain is a free Android app for managing PGP keys and encrypting messages. This guide describes how to install and how to use OpenKeyChain on Android.

Installing OpenKeyChain on Android #

Download OpenKeyChain from Google Play or install it using F-Droid.

If you choose to install via F-Droid, it’s recommended to download and install F-Droid via your computer to ensure you’re downloading from a trusted source. You can find instructions and verify the checksum here: How to install F-Droid.

Once F-Droid is installed, search for OpenKeyChain and install the app.

In OpenKeyChain, privacy-threatening functionalities Key Search and Synchronization are enabled by default. Before further use of the app, make sure that the mentioned features were disabled in the app settings.

Generating keys in OpenKeyChain #

Open the OpenKeyChain app and press +.

Select the Create My Key option.

Enter your nickname and press NEXT.

Enter your non-existent email address and press NEXT.

Click on the three dots and then select Change key configuration.

Change the key’s password, which will be used to protect it, then change the subkeys to RSA 4096bit and press Save.

Set the master key accordingly and press OK.

Set the subkey accordingly and press OK.

Press Save.

Press CREATE KEY.

Wait for the key to be created.

Backing up the private key in OpenKeyChain #

Go to the key management screen, select your private key, and click Backup Key.

Save the backup code, select the location where you want to save the key, and click Save Backup.

Ensure the key is saved in a secure location.

A backup copy of the private key should be encrypted with VeraCrypt or TrueCrypt and placed on external media for protection against data loss.

Importing public keys in OpenKeyChain #

Open the email or other communication containing the public key.

Save the public key to a file with a .asc extension; importing a public key from the clipboard is currently not working.

Open the OpenKeyChain app, select the Import from File option. Select the saved file and click Import.

The app will import the key and display its details.

Encrypting messages in OpenKeyChain #

Open the OpenKeyChain app and select Encrypt/Decrypt.

Select the Encrypt Text option.

Paste or type the text you want to encrypt.
Select the recipient’s public key from the list of available keys. Then choose one of the options from the top bar: Copy to Clipboard or Share.

After encrypting the message, copy the resulting text to the clipboard.
You can now share the encrypted text in another app, such as via an instant messenger or save it to a file.

We do not need to import the public key again when encrypting the next messages. The key will be saved in the application files.

Decrypting messages in OpenKeyChain #

Open the encrypted message in any text editor.
Copy the encrypted text to the clipboard.
Open the OpenKeyChain app and select Encrypt/Decrypt.

Select the Read from Clipboard option. If prompted for a password, enter the password for your private key.

Signing messages in OpenKeyChain #

Open the OpenKeyChain app and select Encrypt/Decrypt, then Encrypt Text.

Select your private key.
Paste the message content you want to sign into the text field, then click Copy or Share.

You can now share the signed text in another app, such as via an instant messenger.

Avoid signing messages that seem universal. For example, a signed “I agree” or “It’s me” message can be saved and used to impersonate you in another conversation. Signed messages should be complete sentences describing the purpose and circumstances of the signature.

Verifying messages in OpenKeyChain #

Open the signed message in any text editor.
Copy its content to the clipboard.

Open the OpenKeyChain app, go to Encrypt/Decrypt, then click Read from Clipboard.

OpenKeyChain will display the verification result, informing you whether the signature is valid.
If the key is not confirmed, it may be highlighted in orange. In such a case:
- Tap on the key owner.
- Tap the three dots in the top-right corner and select Confirm with Fingerprint.
- Check the key’s fingerprint to ensure it matches the expected fingerprint, then confirm the key.

After confirming the key, the verification process should succeed.

We do not need to import the public key again when verifying subsequent signatures of the same author. The key will be saved in the app data files.