Crate hopr_crypto_sphinx

This Rust crate contains implementation of the Sphinx packet format for the HOPR protocol.

SPHINX shared keys derivation

The architecture of the SPHINX shared key derivation is done generically, so it can work with any elliptic curve group for which CDH problem is hard. The generic Sphinx implementation only requires one to implement the SphinxSuite trait.

The trait requires to have the following building blocks:

• elliptic curve group (GroupElement) and corresponding the scalar type (Scalar)
• type representing public and private keypair and their conversion to Scalar and GroupElement (by the means of the corresponding From trait implementation)

Currently, there are the following SphinxSuite implementations :

• Secp256k1Suite: deprecated, used in previous HOPR versions
• Ed25519Suite: simple implementation using Ed25519, used for testing
• X25519Suite currently used, implemented using Curve25519 Montgomery curve for faster computation

The implementation can be easily extended for different elliptic curves (or even arithmetic multiplicative groups). In particular, as soon as there’s way to represent Ed448 PeerIDs, it would be easy to create e.g. an X448Suite.

Modules

derivation

Contains simple key derivation functions for different purposes

ec_groups

Implementations of SphinxSuite trait for different elliptic curve groups

prp

Implementation of the Lioness wide-block cipher using Chacha20 and Blake2b256

routing

Implementation of the SPHINX header format

shared_keys

Derivation of shared keys for SPHINX header