Lock a file on your Android so only its intended recipient can open it. This guide shows how to use OpenKeyChain — a free, open-source OpenPGP app — to create key pairs, exchange public keys by QR or file, and encrypt or sign files so only intended recipients can read them.

Public-key encryption, in plain terms Public-key encryption uses two linked keys: one you keep secret and one you give away. Files encrypted with a recipient's public key can only be opened with that recipient's private key. That means you can stash an encrypted file on your device or send it over chat and be confident no one else can read it. Phil Zimmermann, who created Pretty Good Privacy (PGP) in the early 1990s, set the model for this kind of encryption. The modern, open implementation most people use on desktop systems is GNU Privacy Guard, maintained by Werner Koch. OpenKeyChain brings the same idea to Android. Jack Wallen, a technology writer, notes that OpenKeyChain is free and open-source and makes key management straightforward. The app follows the OpenPGP model, so keys you create or import on Android will interoperate with desktop tools that also follow the standard. That interoperability is important. If you need to send a sensitive document to a colleague who keeps their keys on a laptop, you don't need a special file format or a cloud service: you encrypt with their public key and they decrypt with their private key. Getting started with OpenKeyChain Install the OpenKeyChain app from your chosen Android app repository. Open the app and use the key-management or create-key option. The app walks you through a simple wizard to create your first key pair — you'll choose an identity (name and email), a key type and size, and a passphrase. Use a strong passphrase and store it somewhere safe. Once the key pair exists on your phone, you can publish or export the public key and import public keys from other people. OpenKeyChain supports QR-code exchange: if the person you want to send files to also uses OpenKeyChain, they can display a QR code of their public key and you can scan it directly. If not, they can send you the public-key file which you then import from within the app. Creating a key is only a couple of taps. The first time, spend a minute on the options: choose a reasonably large key size, enable a passphrase, and back up your private key somewhere secure — ideally offline — because if you lose it you'll lose access to anything encrypted to that key. Encrypting and decrypting files Encryption on Android works much like on desktop: pick a file, choose to share it, and select OpenKeyChain or an app that integrates with it. The app will ask which public key(s) to use and produce an encrypted file you can save or send. The result is a file that looks like random data unless you're the intended recipient. To open an encrypted file on the phone that was sent to you, point your file manager or mail app at the file and choose OpenKeyChain to decrypt. The app uses the private key that lives on your device — and only works if you can unlock that key with your passphrase. OpenKeyChain also supports signing files, which proves who created them. Signing is separate from encrypting: you can sign a file so recipients know it came from you, and you can encrypt a file so only the recipient can read it. You can do either or both. Practical workflows and tips - Use the share menu: tap Share in most Android apps, then hand the file to OpenKeyChain for encryption. This keeps the process fast and means you don't need a special file manager. - Scan QR codes for quick key exchange between phones running OpenKeyChain. - Export or publish public keys when you need others to send you encrypted files; always keep your private key backed up somewhere secure, ideally offline.

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OpenKeyChain is free and open-source, and it lets you create and manage OpenPGP key pairs on Android. Import a contact's public key by scanning a QR code or importing a key file, then use the Share menu to encrypt or sign files quickly.

This article was created with AI assistance.