I'm working on an end-to-end encryption system where users can send data to each other; the platform is accessible via web browser and CLI on the user-end. As part of the system, each user locally generates a private/public-key pair on their device (laptop); the private key is used to decrypt incoming data from others.

That said, I'm wondering what and where would be the general practice for storing private keys? — I've considered storing them in Keychain Access (for Mac OS) or in .netrc but then am unsure how to access them on the browser for decryption/signing when time comes for that.