A libp2p transport secure channel handshake built with the Noise Protocol Framework.

Authors: @Mikerah

Interest Group:

See the lifecycle document for context about maturity level and spec status.

The key words "MUST", "SHOULD", "SHOULD NOT", "MAY", "RECOMMENDED", "OPTIONAL", and "REQUIRED" in this document are to be interpreted as described in RFC 2119.

ACN - An anonymous communication network (ACN) is a network designed to provide anonymity to its users.

For descriptions of algorithms and data structures, we use a Go-like pseudocode.

Let k be a security parameter. As recommended in SPHINX09, k should be set to 128.

Let r be the maximum number of nodes that a Sphinx packet will traverse before being sent to its destination. As recommended in SPHINX09, r should be set to 5.

Let G be a prime-order cyclic group that satisfies the Decisional Diffie-Hellman (DDH) assumption.

Let q denote the prime order of G.

Let G* denote the set of non-identity elements in G. In other words, all the elements of G that are not the identity element. We denote the identity element as 1.

Let g be the generator of G. In other words, the order of g is q.

Let H_i(x_1, x_2,..., x_n) denote a hash function where i is some identifier, x_1, x_2,...,x_n are inputs from G* x G* x ... G*, where x is the cartesian product applied n times and H_i(x) is a bit-string.

Let m(x_1, x_2) denote a message authentication code (MAC), where x_1 is a bitstring of size k, x_2 is a bitstring of arbitrary size and m(x_1, x_2) is a bitstring of size k.

Let p(x) denote a pseudo-random generator (PRG), where x is a bistring of size k and p(x) is of size (2r+3)k.

The Sphinx packet format is a provably secure mix format for mix networks and onion routing networks.

This documents specifies sphinx-libp2p, a modification of the sphinx packet format for use with libp2p. As such, it is not a protocol itself, but a building block for building libp2p stacks for ACNs.

Currently, libp2p peers send both plaintext messages and encrypted messages over a libp2p network. However, this isn't sufficient for building secure, anonymous communication protocols on top of libp2p. Many modern designs for ACNs rely on the sphinx packet format. In order to enable the implementation of these proposals on top of libp2p, there needs to be a specification that all libp2p implementations should follow.

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This is the threat model that was presented in (link to OG paper) and (link to Kate and Goldberg paper).

Author's Note: It is, at the moment of this writing, unclear what Libp2p's threat model is. As such, when the threat model for libp2p has been established, this section should be updated to take that into account.

TODO

This section provides guidelines for parameterizing the constants and functions provided in Notation.

These are types are for clarification purposes. Implementers MAY implement these in their language of choice.

type struct RoutingInformation {

}

A Sphinx packet consists of two components: SphinxHeader and SphinxPayload. We define the following data structure as follows:

type struct SphinxPacket {
    header SphinxHeader
    payload SphinxPayload
}

A SphinxHeader is a data structure defined as follows:

type struct SphinxHeader {
    groupElement []byte
    routingInformation []RoutingInformation
    MAC           [k]byte
}

A SphinxPayload is a data structure defined as follows:

type struct SphinxPayload {
    payload []byte
}

TODO

TODO