openvm_pairing_circuit/
pairing_extension.rs

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use derive_more::derive::From;
use num_bigint::BigUint;
use num_traits::{FromPrimitive, Zero};
use openvm_circuit::{
    arch::{VmExtension, VmInventory, VmInventoryBuilder, VmInventoryError},
    system::phantom::PhantomChip,
};
use openvm_circuit_derive::{AnyEnum, InstructionExecutor};
use openvm_circuit_primitives::bitwise_op_lookup::SharedBitwiseOperationLookupChip;
use openvm_circuit_primitives_derive::{Chip, ChipUsageGetter};
use openvm_ecc_circuit::CurveConfig;
use openvm_instructions::PhantomDiscriminant;
use openvm_pairing_guest::{
    bls12_381::{BLS12_381_MODULUS, BLS12_381_ORDER, BLS12_381_XI_ISIZE},
    bn254::{BN254_MODULUS, BN254_ORDER, BN254_XI_ISIZE},
};
use openvm_pairing_transpiler::PairingPhantom;
use openvm_stark_backend::p3_field::PrimeField32;
use serde::{Deserialize, Serialize};
use strum::FromRepr;

use super::*;

// All the supported pairing curves.
#[derive(Clone, Copy, Debug, FromRepr, Serialize, Deserialize)]
#[repr(usize)]
pub enum PairingCurve {
    Bn254,
    Bls12_381,
}

impl PairingCurve {
    pub fn curve_config(&self) -> CurveConfig {
        match self {
            PairingCurve::Bn254 => CurveConfig::new(
                BN254_MODULUS.clone(),
                BN254_ORDER.clone(),
                BigUint::zero(),
                BigUint::from_u8(3).unwrap(),
            ),
            PairingCurve::Bls12_381 => CurveConfig::new(
                BLS12_381_MODULUS.clone(),
                BLS12_381_ORDER.clone(),
                BigUint::zero(),
                BigUint::from_u8(4).unwrap(),
            ),
        }
    }

    pub fn xi(&self) -> [isize; 2] {
        match self {
            PairingCurve::Bn254 => BN254_XI_ISIZE,
            PairingCurve::Bls12_381 => BLS12_381_XI_ISIZE,
        }
    }
}

#[derive(Clone, Debug, derive_new::new, Serialize, Deserialize)]
pub struct PairingExtension {
    pub supported_curves: Vec<PairingCurve>,
}

#[derive(Chip, ChipUsageGetter, InstructionExecutor, AnyEnum)]
pub enum PairingExtensionExecutor<F: PrimeField32> {
    // bn254 (32 limbs)
    MillerDoubleAndAddStepRv32_32(MillerDoubleAndAddStepChip<F, 4, 12, 32>),
    EvaluateLineRv32_32(EvaluateLineChip<F, 4, 2, 4, 32>),
    // bls12-381 (48 limbs)
    MillerDoubleAndAddStepRv32_48(MillerDoubleAndAddStepChip<F, 12, 36, 16>),
    EvaluateLineRv32_48(EvaluateLineChip<F, 12, 6, 12, 16>),
}

#[derive(ChipUsageGetter, Chip, AnyEnum, From)]
pub enum PairingExtensionPeriphery<F: PrimeField32> {
    BitwiseOperationLookup(SharedBitwiseOperationLookupChip<8>),
    Phantom(PhantomChip<F>),
}

impl<F: PrimeField32> VmExtension<F> for PairingExtension {
    type Executor = PairingExtensionExecutor<F>;
    type Periphery = PairingExtensionPeriphery<F>;

    fn build(
        &self,
        builder: &mut VmInventoryBuilder<F>,
    ) -> Result<VmInventory<Self::Executor, Self::Periphery>, VmInventoryError> {
        let inventory = VmInventory::new();

        builder.add_phantom_sub_executor(
            phantom::PairingHintSubEx,
            PhantomDiscriminant(PairingPhantom::HintFinalExp as u16),
        )?;

        Ok(inventory)
    }
}

pub(crate) mod phantom {
    use std::collections::VecDeque;

    use eyre::bail;
    use openvm_circuit::{
        arch::{PhantomSubExecutor, Streams},
        system::memory::MemoryController,
    };
    use openvm_ecc_guest::{algebra::field::FieldExtension, halo2curves::ff, AffinePoint};
    use openvm_instructions::{
        riscv::{RV32_MEMORY_AS, RV32_REGISTER_NUM_LIMBS},
        PhantomDiscriminant,
    };
    use openvm_pairing_guest::{
        bls12_381::BLS12_381_NUM_LIMBS,
        bn254::BN254_NUM_LIMBS,
        pairing::{FinalExp, MultiMillerLoop},
    };
    use openvm_rv32im_circuit::adapters::{compose, unsafe_read_rv32_register};
    use openvm_stark_backend::p3_field::PrimeField32;

    use super::PairingCurve;

    pub struct PairingHintSubEx;

    impl<F: PrimeField32> PhantomSubExecutor<F> for PairingHintSubEx {
        fn phantom_execute(
            &mut self,
            memory: &MemoryController<F>,
            streams: &mut Streams<F>,
            _: PhantomDiscriminant,
            a: F,
            b: F,
            c_upper: u16,
        ) -> eyre::Result<()> {
            let rs1 = unsafe_read_rv32_register(memory, a);
            let rs2 = unsafe_read_rv32_register(memory, b);
            hint_pairing(memory, &mut streams.hint_stream, rs1, rs2, c_upper)
        }
    }

    fn hint_pairing<F: PrimeField32>(
        memory: &MemoryController<F>,
        hint_stream: &mut VecDeque<F>,
        rs1: u32,
        rs2: u32,
        c_upper: u16,
    ) -> eyre::Result<()> {
        let p_ptr = compose(memory.unsafe_read(
            F::from_canonical_u32(RV32_MEMORY_AS),
            F::from_canonical_u32(rs1),
        ));
        // len in bytes
        let p_len = compose(memory.unsafe_read(
            F::from_canonical_u32(RV32_MEMORY_AS),
            F::from_canonical_u32(rs1 + RV32_REGISTER_NUM_LIMBS as u32),
        ));
        let q_ptr = compose(memory.unsafe_read(
            F::from_canonical_u32(RV32_MEMORY_AS),
            F::from_canonical_u32(rs2),
        ));
        // len in bytes
        let q_len = compose(memory.unsafe_read(
            F::from_canonical_u32(RV32_MEMORY_AS),
            F::from_canonical_u32(rs2 + RV32_REGISTER_NUM_LIMBS as u32),
        ));

        match PairingCurve::from_repr(c_upper as usize) {
            Some(PairingCurve::Bn254) => {
                use openvm_ecc_guest::halo2curves::bn256::{Fq, Fq12, Fq2};
                use openvm_pairing_guest::halo2curves_shims::bn254::Bn254;
                const N: usize = BN254_NUM_LIMBS;
                if p_len != q_len {
                    bail!("hint_pairing: p_len={p_len} != q_len={q_len}");
                }
                let p = (0..p_len)
                    .map(|i| -> eyre::Result<_> {
                        let ptr = p_ptr + i * 2 * (N as u32);
                        let x = read_fp::<N, F, Fq>(memory, ptr)?;
                        let y = read_fp::<N, F, Fq>(memory, ptr + N as u32)?;
                        Ok(AffinePoint::new(x, y))
                    })
                    .collect::<eyre::Result<Vec<_>>>()?;
                let q = (0..q_len)
                    .map(|i| -> eyre::Result<_> {
                        let mut ptr = q_ptr + i * 4 * (N as u32);
                        let mut read_fp2 = || -> eyre::Result<_> {
                            let c0 = read_fp::<N, F, Fq>(memory, ptr)?;
                            let c1 = read_fp::<N, F, Fq>(memory, ptr + N as u32)?;
                            ptr += 2 * N as u32;
                            Ok(Fq2::new(c0, c1))
                        };
                        let x = read_fp2()?;
                        let y = read_fp2()?;
                        Ok(AffinePoint::new(x, y))
                    })
                    .collect::<eyre::Result<Vec<_>>>()?;

                let f: Fq12 = Bn254::multi_miller_loop(&p, &q);
                let (c, u) = Bn254::final_exp_hint(&f);
                hint_stream.clear();
                hint_stream.extend(
                    c.to_coeffs()
                        .into_iter()
                        .chain(u.to_coeffs())
                        .flat_map(|fp2| fp2.to_coeffs())
                        .flat_map(|fp| fp.to_bytes())
                        .map(F::from_canonical_u8),
                );
            }
            Some(PairingCurve::Bls12_381) => {
                use openvm_ecc_guest::halo2curves::bls12_381::{Fq, Fq12, Fq2};
                use openvm_pairing_guest::halo2curves_shims::bls12_381::Bls12_381;
                const N: usize = BLS12_381_NUM_LIMBS;
                if p_len != q_len {
                    bail!("hint_pairing: p_len={p_len} != q_len={q_len}");
                }
                let p = (0..p_len)
                    .map(|i| -> eyre::Result<_> {
                        let ptr = p_ptr + i * 2 * (N as u32);
                        let x = read_fp::<N, F, Fq>(memory, ptr)?;
                        let y = read_fp::<N, F, Fq>(memory, ptr + N as u32)?;
                        Ok(AffinePoint::new(x, y))
                    })
                    .collect::<eyre::Result<Vec<_>>>()?;
                let q = (0..q_len)
                    .map(|i| -> eyre::Result<_> {
                        let mut ptr = q_ptr + i * 4 * (N as u32);
                        let mut read_fp2 = || -> eyre::Result<_> {
                            let c0 = read_fp::<N, F, Fq>(memory, ptr)?;
                            let c1 = read_fp::<N, F, Fq>(memory, ptr + N as u32)?;
                            ptr += 2 * N as u32;
                            Ok(Fq2 { c0, c1 })
                        };
                        let x = read_fp2()?;
                        let y = read_fp2()?;
                        Ok(AffinePoint::new(x, y))
                    })
                    .collect::<eyre::Result<Vec<_>>>()?;

                let f: Fq12 = Bls12_381::multi_miller_loop(&p, &q);
                let (c, u) = Bls12_381::final_exp_hint(&f);
                hint_stream.clear();
                hint_stream.extend(
                    c.to_coeffs()
                        .into_iter()
                        .chain(u.to_coeffs())
                        .flat_map(|fp2| fp2.to_coeffs())
                        .flat_map(|fp| fp.to_bytes())
                        .map(F::from_canonical_u8),
                );
            }
            _ => {
                bail!("hint_pairing: invalid PairingCurve={c_upper}");
            }
        }
        Ok(())
    }

    fn read_fp<const N: usize, F: PrimeField32, Fp: ff::PrimeField>(
        memory: &MemoryController<F>,
        ptr: u32,
    ) -> eyre::Result<Fp>
    where
        Fp::Repr: From<[u8; N]>,
    {
        let mut repr = [0u8; N];
        for (i, byte) in repr.iter_mut().enumerate() {
            *byte = memory
                .unsafe_read_cell(
                    F::from_canonical_u32(RV32_MEMORY_AS),
                    F::from_canonical_u32(ptr + i as u32),
                )
                .as_canonical_u32()
                .try_into()?;
        }
        Fp::from_repr(repr.into())
            .into_option()
            .ok_or(eyre::eyre!("bad ff::PrimeField repr"))
    }
}