NIP-104

Double Ratchet E2EE Direct Messages

This NIP defines an encrypted direct messaging scheme that provides double-ratchet E2EE (end-to-end encryption) with forward secrecy & post-compromise (backward) secrecy and allows users to access messages from multiple synced devices.

• Live demo
• Demo app code
• Demo app video with explainer

Context

Currently, one-to-one direct messages (DMs) in Nostr happen via the scheme defined in NIP-04. This NIP is not recommended because, while it encrypts the content of the message, it leaks significant amounts of metadata about the parties involved in the conversation.

With the addition of NIP-44, we have an updated encryption scheme that improves some (but not all) of the metadata leakage and improves the obfuscation of message content but this NIP stops short of defining a new kind number or scheme for doing direct messages using this encryption scheme.

There have been a few separate proposals for new ways to do DMs that do not leak metadata. The most accepted (and recently merged) one is NIP-17 which combines NIP-44 encryption with NIP-59 gift-wrapping to hide the actual direct message inside another set of events to ensure that it's impossible to see who is talking to who and when messages passed between the users. This solves the metadata leakage problem and does allow some degree of deniability/repudiation but doesn't solve forward/backward secrecy. That is to say, if a user's private key (or the calculated conversation key used to encrypt messages) is compromised, the attacker will have full access to all past and future DMs sent between those users.

... read more