ethdss

Documentation

Overview

Package ethdss implements the Distributed Schnorr Signature protocol from the //////////////////////////////////////////////////////////////////////////////

XXX: Do not use in production until this code has been audited.

////////////////////////////////////////////////////////////////////////////// paper "Provably Secure Distributed Schnorr Signatures and a (t, n) Threshold Scheme for Implicit Certificates". https://dl.acm.org/citation.cfm?id=678297 To generate a distributed signature from a group of participants, the group must first generate one longterm distributed secret with the share/dkg package, and then one random secret to be used only once. Each participant then creates a DSS struct, that can issue partial signatures with `dss.PartialSignature()`. These partial signatures can be broadcasted to the whole group or to a trusted combiner. Once one has collected enough partial signatures, it is possible to compute the distributed signature with the `Signature` method.

This is mostly copied from the sign/dss package, with minor adjustments for use with ethschnorr.

Index

• func Verify(public kyber.Point, msg *big.Int, sig ethschnorr.Signature) error
• type DSS
  • func NewDSS(args DSSArgs) (*DSS, error)
  • func (d *DSS) EnoughPartialSig() bool
  • func (d *DSS) PartialSig() (*PartialSig, error)
  • func (d *DSS) ProcessPartialSig(ps *PartialSig) error
  • func (d *DSS) Signature() (ethschnorr.Signature, error)
• type DSSArgs
• type DistKeyShare
• type PartialSig
  • func (ps *PartialSig) Hash() *big.Int
• type Suite

Functions

func Verify

func Verify(public kyber.Point, msg *big.Int, sig ethschnorr.Signature) error

Verify takes a public key, a message and a signature and returns an error if the signature is invalid.

Types

type DSS

type DSS struct {

	// Number of participants needed to construct a signature
	T int
	// contains filtered or unexported fields
}

DSS holds the information used to issue partial signatures as well as to compute the distributed schnorr signature.

func NewDSS

func NewDSS(args DSSArgs) (*DSS, error)

NewDSS returns a DSS struct out of the suite, the longterm secret of this node, the list of participants, the longterm and random distributed key (generated by the dkg package), the message to sign and finally the T threshold. It returns an error if the public key of the secret can't be found in the list of participants.

func (*DSS) EnoughPartialSig

func (d *DSS) EnoughPartialSig() bool

EnoughPartialSig returns true if there are enough partial signature to compute the distributed signature. It returns false otherwise. If there are enough partial signatures, one can issue the signature with `Signature()`.

func (*DSS) PartialSig

func (d *DSS) PartialSig() (*PartialSig, error)

PartialSig generates the partial signature related to this DSS. This PartialSig can be broadcasted to every other participant or only to a trusted combiner as described in the paper. The signature format is compatible with EdDSA verification implementations.

Corresponds to section 4.2, step 2 the Stinson 2001 paper.

func (*DSS) ProcessPartialSig

func (d *DSS) ProcessPartialSig(ps *PartialSig) error

ProcessPartialSig takes a PartialSig from another participant and stores it for generating the distributed signature. It returns an error if the index is wrong, or the signature is invalid or if a partial signature has already been received by the same peer. To know whether the distributed signature can be computed after this call, one can use the `EnoughPartialSigs` method.

Corresponds to section 4.3, step 3 of the paper

func (*DSS) Signature

func (d *DSS) Signature() (ethschnorr.Signature, error)

Signature computes the distributed signature from the list of partial signatures received. It returns an error if there are not enough partial signatures.

Corresponds to section 4.2, step 4 of Stinson, 2001 paper

type DSSArgs

type DSSArgs = struct {
	T int
	// contains filtered or unexported fields
}

DSSArgs is the arguments to NewDSS, as a struct. See NewDSS for details.

type DistKeyShare

type DistKeyShare interface {
	PriShare() *share.PriShare
	Commitments() []kyber.Point
}

DistKeyShare is an abstraction to allow one to use distributed key share from different schemes easily into this distributed threshold Schnorr signature framework.

type PartialSig

type PartialSig struct {
	Partial   *share.PriShare
	SessionID []byte
	Signature ethschnorr.Signature
}

PartialSig is partial representation of the final distributed signature. It must be sent to each of the other participants.

func (*PartialSig) Hash

func (ps *PartialSig) Hash() *big.Int

Hash returns the hash representation of this PartialSig to be used in a signature.

type Suite

type Suite interface {
	kyber.Group
	kyber.HashFactory
	kyber.Random
}

Suite represents the functionalities needed by the dss package