poseidon2

Documentation

Overview

Package poseidon2 implements the Poseidon2 permutation

Poseidon2 permutation is a cryptographic permutation for algebraic hashes. See the original paper by Grassi, Khovratovich and Schofnegger for the full details.

This implementation is based on the reference implementation from HorizenLabs. See the specifications for parameter choices.

Index

• Variables
• func DegreeSBox() int
• func NewMerkleDamgardHasher() gnarkHash.StateStorer
• type Parameters
  • func NewParameters(width, nbFullRounds, nbPartialRounds int) *Parameters
  • func NewParametersWithSeed(width, nbFullRounds, nbPartialRounds int, seed string) *Parameters
  • func (p *Parameters) String() string
• type Permutation
  • func NewPermutation(t, rf, rp int) *Permutation
  • func NewPermutationWithSeed(t, rf, rp int, seed string) *Permutation
  • func (h *Permutation) BlockSize() int
  • func (h *Permutation) Compress(left []byte, right []byte) ([]byte, error)
  • func (h *Permutation) Permutation(input []fr.Element) error

Variables

var (
	ErrInvalidSizebuffer = errors.New("the size of the input should match the size of the hash buffer")
)

var GetDefaultParameters = sync.OnceValue(func() *Parameters {
	return NewParameters(2, 6, 40)
})

GetDefaultParameters returns a set of parameters for the Poseidon2 permutation. The default parameters are: - width: 2 for compression 3 for sponge - nbFullRounds: 6 - nbPartialRounds: 26

Functions

func DegreeSBox

func DegreeSBox() int

DegreeSBox returns the degree of the sBox function used in the Poseidon2 permutation.

func NewMerkleDamgardHasher

func NewMerkleDamgardHasher() gnarkHash.StateStorer

NewMerkleDamgardHasher returns a Poseidon2 hasher using the Merkle-Damgard construction with the default parameters.

Types

type Parameters

type Parameters struct {
	// len(preimage)+len(digest)=len(preimage)+ceil(log(2*<security_level>/r))
	Width int

	// number of full rounds (even number)
	NbFullRounds int

	// number of partial rounds
	NbPartialRounds int

	// derived round keys from the parameter seed and curve ID
	RoundKeys [][]fr.Element
}

Parameters describing the Poseidon2 implementation. Use NewParameters or NewParametersWithSeed to initialize a new set of parameters to deterministically precompute the round keys.

func NewParameters

func NewParameters(width, nbFullRounds, nbPartialRounds int) *Parameters

NewParameters returns a new set of parameters for the Poseidon2 permutation. After creating the parameters, the round keys are initialized deterministically from the seed which is a digest of the parameters and curve ID.

func NewParametersWithSeed

func NewParametersWithSeed(width, nbFullRounds, nbPartialRounds int, seed string) *Parameters

NewParametersWithSeed returns a new set of parameters for the Poseidon2 permutation. After creating the parameters, the round keys are initialized deterministically from the given seed.

func (*Parameters) String

func (p *Parameters) String() string

String returns a string representation of the parameters. It is unique for specific parameters and curve.

type Permutation

type Permutation struct {
	// contains filtered or unexported fields
}

Permutation stores the buffer of the Poseidon2 permutation and provides Poseidon2 permutation methods on the buffer

func NewPermutation

func NewPermutation(t, rf, rp int) *Permutation

NewPermutation returns a new Poseidon2 permutation instance.

func NewPermutationWithSeed

func NewPermutationWithSeed(t, rf, rp int, seed string) *Permutation

NewPermutationWithSeed returns a new Poseidon2 permutation instance with a given seed.

func (*Permutation) BlockSize

func (h *Permutation) BlockSize() int

func (*Permutation) Compress

func (h *Permutation) Compress(left []byte, right []byte) ([]byte, error)

Compress uses the permutation to compress the left and right input in a collision resistant manner. Returns an error if the permutation instance is not initialized with a width of 2.

func (*Permutation) Permutation

func (h *Permutation) Permutation(input []fr.Element) error

Permutation applies the permutation on input, and stores the result in input.