GnuPG allows you to encrypt and sign your data and communications. Following are download links for different platforms. Mac: GPG Suite. OpenKeychain for Android: Google Play and F-Droid.
Email Encryption
gnupg.org
Our take
GnuPG remains the standard for encrypting and signing files and mail, and nothing else has its longevity or interoperability. Be honest about the experience: key management is genuinely hard, and the well-known usability problems are why most people quietly abandon PGP email. Worth learning if you must exchange signed or encrypted messages with others who already use it; for private conversation, a modern messenger is far easier to live with.
Listed in
Email Encryption alternatives
VERNAM A free, fully client-side file encryptor that runs in your browser. Drop in any file, set or generate a passphrase, and it seals the result into its own .vrn format. Nothing is ever uploaded, and it works offline.
PrivacyNotes Zero-knowledge notes, tasks, files, passwords and journal secured by a single 12-word recovery phrase, with no email or password required. The crypto core and database schema are published for audit. No subscription model.
VeraCrypt It can create a virtual encrypted disk that works just like a regular disk but within a file. It can also encrypt a partition or the entire storage device with pre-boot…
Cryptomator Cryptomator encrypts your data quickly and easily. Afterwards you upload them protected to a cloud service.
LUKS LUKS (Linux Unified Key Setup) is the standard disk-encryption specification for Linux, implemented by the cryptsetup utility. It provides a header format and key-slot system on top of the dm-crypt kernel module, supporting multiple decryption passphrases per volume.
GnuPG GnuPG (GNU Privacy Guard) is the free, GPL-licensed implementation of the OpenPGP standard. A command-line tool for Linux, macOS, and Windows, it encrypts and signs files and email, and manages public-key directories.