subsoil 0.2.0

Soil primitives foundation crate
Documentation 
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// This file is part of Soil.

// Copyright (C) Soil contributors.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0 OR GPL-3.0-or-later WITH Classpath-exception-2.0

//! *Ed-on-BLS12-377* types and host functions.

use super::utils::{self, HostcallResult, FAIL_MSG};
use crate::runtime_interface::{
	pass_by::{PassFatPointerAndRead, PassFatPointerAndWrite},
	runtime_interface,
};
use alloc::vec::Vec;
use ark_ec::{AffineRepr, CurveConfig, CurveGroup};
use ark_ed_on_bls12_377_ext::CurveHooks;

/// Group configuration.
pub type EdwardsConfig = ark_ed_on_bls12_377_ext::EdwardsConfig<HostHooks>;
/// Twisted Edwards form point affine representation.
pub type EdwardsAffine = ark_ed_on_bls12_377_ext::EdwardsAffine<HostHooks>;
/// Twisted Edwards form point projective representation.
pub type EdwardsProjective = ark_ed_on_bls12_377_ext::EdwardsProjective<HostHooks>;

/// Group scalar field (Fr).
pub type ScalarField = <EdwardsConfig as CurveConfig>::ScalarField;

/// Curve hooks jumping into [`host_calls`] host functions.
#[derive(Copy, Clone)]
pub struct HostHooks;

impl CurveHooks for HostHooks {
	fn msm(bases: &[EdwardsAffine], scalars: &[ScalarField]) -> EdwardsProjective {
		let mut out = utils::buffer_for::<EdwardsAffine>();
		host_calls::ed_on_bls12_377_msm(&utils::encode(bases), &utils::encode(scalars), &mut out)
			.and_then(|_| utils::decode::<EdwardsAffine>(&out))
			.expect(FAIL_MSG)
			.into_group()
	}

	fn mul_projective(base: &EdwardsProjective, scalar: &[u64]) -> EdwardsProjective {
		let mut out = utils::buffer_for::<EdwardsAffine>();
		host_calls::ed_on_bls12_377_mul(
			&utils::encode(base.into_affine()),
			&utils::encode(scalar),
			&mut out,
		)
		.and_then(|_| utils::decode::<EdwardsAffine>(&out))
		.expect(FAIL_MSG)
		.into_group()
	}
}

/// Interfaces for working with *Arkworks* *Ed-on-BLS12-377* elliptic curve related types
/// from within the runtime.
///
/// All types are (de-)serialized through the wrapper types from `ark-scale`.
///
/// `ArkScale`'s `Usage` generic parameter is expected to be set to "not-validated"
/// and "not-compressed".
#[runtime_interface]
pub trait HostCalls {
	/// Twisted Edwards multi scalar multiplication for *Ed-on-BLS12-377*.
	///
	/// Receives encoded:
	/// - `bases`: `Vec<EdwardsAffine>`.
	/// - `scalars`: `Vec<ScalarField>`.
	/// Writes encoded `EdwardsAffine` to `out`.
	fn ed_on_bls12_377_msm(
		bases: PassFatPointerAndRead<&[u8]>,
		scalars: PassFatPointerAndRead<&[u8]>,
		out: PassFatPointerAndWrite<&mut [u8]>,
	) -> HostcallResult {
		utils::msm_te::<ark_ed_on_bls12_377::EdwardsConfig>(bases, scalars, out)
	}

	/// Twisted Edwards affine multiplication for *Ed-on-BLS12-377*.
	///
	/// Receives encoded:
	/// - `base`: `EdwardsAffine`.
	/// - `scalar`: `BigInteger`.
	/// Writes encoded `EdwardsAffine` to `out`.
	fn ed_on_bls12_377_mul(
		base: PassFatPointerAndRead<&[u8]>,
		scalar: PassFatPointerAndRead<&[u8]>,
		out: PassFatPointerAndWrite<&mut [u8]>,
	) -> HostcallResult {
		utils::mul_te::<ark_ed_on_bls12_377::EdwardsConfig>(base, scalar, out)
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use crate::crypto_ec_utils::utils::testing::*;

	#[test]
	fn mul_works() {
		mul_te_test::<EdwardsAffine, ark_ed_on_bls12_377::EdwardsAffine>();
	}

	#[test]
	fn msm_works() {
		msm_te_test::<EdwardsAffine, ark_ed_on_bls12_377::EdwardsAffine>();
	}
}