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Merge pull request #244 from dusk-network/mocello/243_refactor_hades
Refactor hades and only expose `WIDTH`
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// This Source Code Form is subject to the terms of the Mozilla Public | ||
// License, v. 2.0. If a copy of the MPL was not distributed with this | ||
// file, You can obtain one at http://mozilla.org/MPL/2.0/. | ||
// | ||
// Copyright (c) DUSK NETWORK. All rights reserved. | ||
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//! This module contains an implementation of the `Hades252` permutation | ||
//! algorithm specifically designed to work outside of Rank 1 Constraint Systems | ||
//! (R1CS) or other custom Constraint Systems such as Add/Mul/Custom plonk | ||
//! gate-circuits. | ||
//! | ||
//! The inputs of the permutation function have to be explicitly over the | ||
//! scalar Field of the bls12_381 curve so over a modulus | ||
//! `p = 0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001`. | ||
use dusk_bls12_381::BlsScalar; | ||
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#[cfg(feature = "zk")] | ||
use dusk_plonk::prelude::{Composer, Witness}; | ||
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use crate::hades::{PARTIAL_ROUNDS, ROUND_CONSTANTS, TOTAL_FULL_ROUNDS, WIDTH}; | ||
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/// State for zero-knowledge plonk circuits | ||
#[cfg(feature = "zk")] | ||
mod gadget; | ||
#[cfg(feature = "zk")] | ||
use gadget::GadgetPermutaiton; | ||
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/// State for scalar | ||
mod scalar; | ||
use scalar::ScalarPermutation; | ||
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/// Applies one Hades permutation to the state operating on the scalar-field of | ||
/// the bls12_381 elliptic curve. | ||
/// | ||
/// This permutation is a 3-step process that: | ||
/// - Applies half of the `FULL_ROUNDS` (which can be understood as linear ops). | ||
/// - Applies the `PARTIAL_ROUDS` (which can be understood as non-linear ops). | ||
/// - Applies the other half of the `FULL_ROUNDS`. | ||
/// | ||
/// This structure allows to minimize the number of non-linear ops while | ||
/// mantaining the security. | ||
pub(crate) fn permute(state: &mut [BlsScalar; WIDTH]) { | ||
let mut hades = ScalarPermutation::new(); | ||
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hades.perm(state); | ||
} | ||
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/// Applies one Hades permutation on the given state in a plonk circuit. | ||
/// | ||
/// This permutation is a 3-step process that: | ||
/// - Applies half of the `FULL_ROUNDS` (which can be understood as linear ops). | ||
/// - Applies the `PARTIAL_ROUDS` (which can be understood as non-linear ops). | ||
/// - Applies the other half of the `FULL_ROUNDS`. | ||
/// | ||
/// This structure allows to minimize the number of non-linear ops while | ||
/// mantaining the security. | ||
#[cfg(feature = "zk")] | ||
pub(crate) fn permute_gadget( | ||
composer: &mut Composer, | ||
state: &mut [Witness; WIDTH], | ||
) { | ||
let mut hades = GadgetPermutaiton::new(composer); | ||
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hades.perm(state); | ||
} | ||
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/// Defines the Hades252 permutation algorithm. | ||
pub(crate) trait Permutation<T> { | ||
/// Fetch the next round constant from an iterator | ||
fn next_c<'b, I>(constants: &mut I) -> BlsScalar | ||
where | ||
I: Iterator<Item = &'b BlsScalar>, | ||
{ | ||
constants | ||
.next() | ||
.copied() | ||
.expect("Hades252 shouldn't be out of ARK constants") | ||
} | ||
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/// Add round keys to the state. | ||
/// | ||
/// This round key addition, also known as `ARK`, is used to reach | ||
/// `Confusion and Diffusion` properties for the algorithm. | ||
/// | ||
/// Basically it allows to destroy any connection between the inputs and the | ||
/// outputs of the function. | ||
fn add_round_key<'b, I>( | ||
&mut self, | ||
constants: &mut I, | ||
state: &mut [T; WIDTH], | ||
) where | ||
I: Iterator<Item = &'b BlsScalar>; | ||
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/// Computes `input ^ 5 (mod p)` | ||
/// | ||
/// The modulo depends on the input you use. In our case the modulo is done | ||
/// in respect of the scalar field of the bls12_381 curve | ||
/// `p = 0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001`. | ||
fn quintic_s_box(&mut self, value: &mut T); | ||
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/// Multiply the MDS matrix with the state. | ||
fn mul_matrix<'b, I>(&mut self, constants: &mut I, state: &mut [T; WIDTH]) | ||
where | ||
I: Iterator<Item = &'b BlsScalar>; | ||
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/// Applies a `Partial Round` also known as a `Partial S-Box layer` to a set | ||
/// of inputs. | ||
/// | ||
/// One partial round consists of 3 steps: | ||
/// - ARK: Add round keys constants to each state element. | ||
/// - Sub State: Apply `quintic S-Box` just to **the last element of the | ||
/// state** generated from the first step. | ||
/// - Mix Layer: Multiplies the output state from the second step by the | ||
/// `MDS_MATRIX`. | ||
fn apply_partial_round<'b, I>( | ||
&mut self, | ||
constants: &mut I, | ||
state: &mut [T; WIDTH], | ||
) where | ||
I: Iterator<Item = &'b BlsScalar>, | ||
{ | ||
// Add round keys to each state element | ||
self.add_round_key(constants, state); | ||
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// Then apply quintic s-box | ||
self.quintic_s_box(&mut state[WIDTH - 1]); | ||
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// Multiply this result by the MDS matrix | ||
self.mul_matrix(constants, state); | ||
} | ||
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/// Applies a `Full Round` also known as a `Full S-Box layer` to a set of | ||
/// inputs. | ||
/// | ||
/// One full round constists of 3 steps: | ||
/// - ARK: Add round keys to each state element. | ||
/// - Sub State: Apply `quintic S-Box` to **all of the state-elements** | ||
/// generated from the first step. | ||
/// - Mix Layer: Multiplies the output state from the second step by the | ||
/// `MDS_MATRIX`. | ||
fn apply_full_round<'a, I>( | ||
&mut self, | ||
constants: &mut I, | ||
state: &mut [T; WIDTH], | ||
) where | ||
I: Iterator<Item = &'a BlsScalar>, | ||
{ | ||
// Add round keys to each state element | ||
self.add_round_key(constants, state); | ||
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// Then apply quintic s-box | ||
state.iter_mut().for_each(|w| self.quintic_s_box(w)); | ||
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// Multiply this result by the MDS matrix | ||
self.mul_matrix(constants, state); | ||
} | ||
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/// Applies one Hades permutation. | ||
/// | ||
/// This permutation is a 3-step process that: | ||
/// - Applies half of the `FULL_ROUNDS` (which can be understood as linear | ||
/// ops). | ||
/// - Applies the `PARTIAL_ROUDS` (which can be understood as non-linear | ||
/// ops). | ||
/// - Applies the other half of the `FULL_ROUNDS`. | ||
/// | ||
/// This structure allows to minimize the number of non-linear ops while | ||
/// mantaining the security. | ||
fn perm(&mut self, state: &mut [T; WIDTH]) { | ||
let mut constants = ROUND_CONSTANTS.iter(); | ||
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// Apply R_f full rounds | ||
for _ in 0..TOTAL_FULL_ROUNDS / 2 { | ||
self.apply_full_round(&mut constants, state); | ||
} | ||
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// Apply R_P partial rounds | ||
for _ in 0..PARTIAL_ROUNDS { | ||
self.apply_partial_round(&mut constants, state); | ||
} | ||
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// Apply R_f full rounds | ||
for _ in 0..TOTAL_FULL_ROUNDS / 2 { | ||
self.apply_full_round(&mut constants, state); | ||
} | ||
} | ||
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/// Return the total rounds count | ||
fn rounds() -> usize { | ||
TOTAL_FULL_ROUNDS + PARTIAL_ROUNDS | ||
} | ||
} |
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