Javascript public/private key encryption

Question

I'd like to generate a public/private keypair in javascript, and use the public key to encrypt message and the private key to decrypt the message.

I prefer native browser support over external libraries. How can I do this in JavaScript?

Modern browsers implement window.crypto.subtle.generateKey. I can use it to generate ECDSA private/public keys to sign/verify messages, this works. But I cannot find a way how to use it to generate pub/private keys to encrypt/decrypt. If I try the generateKey for the recommended AES-GCM Algorithm, it generates just one cryptoKey, which can be probably used to both encrypt and decrypt. But I prefer to get a keypair (publib/private keys), not just a single key. Any suggestions?

This table lists currently supported methods, but it seems none of the green algorithms is what I need: https://diafygi.github.io/webcrypto-examples/

Answer 1

Due to ProtonMail's efforts, there is now an open source Symmetric Key Encryption implementation in the browser at: https://openpgpjs.org/

This has had multiple security audits and is the basis of protonmail.com, so it has a fairly good records and maintainer in place. They also have a good summary of important security browser models.