Noise is a framework that can be used to construct secure channel protocols. Noise takes a fairly basic set of cryptographic operations and allows the

An Introduction to the Noise Protocol Framework

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2023-05-30 11:30:03

Noise is a framework that can be used to construct secure channel protocols. Noise takes a fairly basic set of cryptographic operations and allows them to be combined in ways that provide various security properties. Noise is not a protocol itself: it is a protocol framework, so by "filling in the blanks" you get a concrete protocol that has essentially no knobs to twist. We’ll use the term “Noise protocol” to refer to a concrete protocol, and “Noise framework” to refer to the framework overall.

Every Noise protocol begins with a handshake that follows a particular pattern. The end result of a Noise handshake is an encrypted channel that provides various forms of confidentiality, integrity, and authenticity guarantees. Which of these guarantees you get depends on which handshake pattern is used, but a collection of standard handshakes with known security properties are provided. The Noise framework is fully agnostic to what is actually transmitted via the encrypted channel established with a handshake. You could transmit messages, video files, or anything else.

Noise is fundamentally based around Diffie-Hellman key agreement. There are many constructions that make use of DH, including perhaps the most simple DH construction which is to agree on a key that is then used directly for symmetric encryption. Noise has several advantages over building your own DH-based protocol. Some of the primary benefits are (1) that the structured nature of the Noise framework allows us to build protocols with exactly the properties we need, as well as analyze whether those properties are present, and (2) that “advanced” properties not provided by a simple DH construction (like message authentication) can be built into Noise protocols with combinations of Diffie-Hellman and the behavior of the Noise state machine. Noise Explorer is a tool that automatically analyzes handshake patterns and demonstrates the security guarantees present at each step of the handshake graphically. I refer to Noise Explorer often when trying to understand new handshake patterns.