Add Grumpkin support for arkworks (#174)

Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

grumpkin/src/constraints/curves.rs

@@ -0,0 +1,11 @@
+use ark_r1cs_std::groups::curves::short_weierstrass::ProjectiveVar;
+
+use crate::{constraints::FBaseVar, *};
+
+/// A group element in the Grumpkin prime-order group.
+pub type GVar = ProjectiveVar<GrumpkinConfig, FBaseVar>;
+
+#[test]
+fn test() {
+    ark_curve_constraint_tests::curves::sw_test::<GrumpkinConfig, GVar>().unwrap();
+}

grumpkin/src/constraints/fields.rs

@@ -0,0 +1,11 @@
+use ark_r1cs_std::fields::fp::FpVar;
+
+use crate::fq::Fq;
+
+/// A variable that is the R1CS equivalent of `crate::Fq`.
+pub type FBaseVar = FpVar<Fq>;
+
+#[test]
+fn test() {
+    ark_curve_constraint_tests::fields::field_test::<_, _, FBaseVar>().unwrap();
+}

grumpkin/src/constraints/mod.rs

@@ -0,0 +1,107 @@
+//! This module implements the R1CS equivalent of `ark_grumpkin`.
+//!
+//! It implements field variables for `crate::Fq`,
+//! and group variables for `crate::Projective`.
+//!
+//! The field underlying these constraints is `crate::Fq`.
+//!
+//! # Examples
+//!
+//! One can perform standard algebraic operations on `FBaseVar`:
+//!
+//! ```
+//! # fn main() -> Result<(), ark_relations::r1cs::SynthesisError> {
+//! use ark_std::UniformRand;
+//! use ark_relations::r1cs::*;
+//! use ark_r1cs_std::prelude::*;
+//! use ark_grumpkin::{*, constraints::*};
+//!
+//! let cs = ConstraintSystem::<Fq>::new_ref();
+//! // This rng is just for test purposes; do not use it
+//! // in real applications.
+//! let mut rng = ark_std::test_rng();
+//!
+//! // Generate some random `Fq` elements.
+//! let a_native = Fq::rand(&mut rng);
+//! let b_native = Fq::rand(&mut rng);
+//!
+//! // Allocate `a_native` and `b_native` as witness variables in `cs`.
+//! let a = FBaseVar::new_witness(ark_relations::ns!(cs, "generate_a"), || Ok(a_native))?;
+//! let b = FBaseVar::new_witness(ark_relations::ns!(cs, "generate_b"), || Ok(b_native))?;
+//!
+//! // Allocate `a_native` and `b_native` as constants in `cs`. This does not add any
+//! // constraints or variables.
+//! let a_const = FBaseVar::new_constant(ark_relations::ns!(cs, "a_as_constant"), a_native)?;
+//! let b_const = FBaseVar::new_constant(ark_relations::ns!(cs, "b_as_constant"), b_native)?;
+//!
+//! let one = FBaseVar::one();
+//! let zero = FBaseVar::zero();
+//!
+//! // Sanity check one + one = two
+//! let two = &one + &one + &zero;
+//! two.enforce_equal(&one.double()?)?;
+//!
+//! assert!(cs.is_satisfied()?);
+//!
+//! // Check that the value of &a + &b is correct.
+//! assert_eq!((&a + &b).value()?, a_native + &b_native);
+//!
+//! // Check that the value of &a * &b is correct.
+//! assert_eq!((&a * &b).value()?, a_native * &b_native);
+//!
+//! // Check that operations on variables and constants are equivalent.
+//! (&a + &b).enforce_equal(&(&a_const + &b_const))?;
+//! assert!(cs.is_satisfied()?);
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! One can also perform standard algebraic operations on `GVar`:
+//!
+//! ```
+//! # fn main() -> Result<(), ark_relations::r1cs::SynthesisError> {
+//! # use ark_std::UniformRand;
+//! # use ark_relations::r1cs::*;
+//! # use ark_r1cs_std::prelude::*;
+//! # use ark_grumpkin::{*, constraints::*};
+//!
+//! # let cs = ConstraintSystem::<Fq>::new_ref();
+//! # let mut rng = ark_std::test_rng();
+//!
+//! // Generate some random `Projective` elements.
+//! let a_native = Projective::rand(&mut rng);
+//! let b_native = Projective::rand(&mut rng);
+//!
+//! // Allocate `a_native` and `b_native` as witness variables in `cs`.
+//! let a = GVar::new_witness(ark_relations::ns!(cs, "a"), || Ok(a_native))?;
+//! let b = GVar::new_witness(ark_relations::ns!(cs, "b"), || Ok(b_native))?;
+//!
+//! // Allocate `a_native` and `b_native` as constants in `cs`. This does not add any
+//! // constraints or variables.
+//! let a_const = GVar::new_constant(ark_relations::ns!(cs, "a_as_constant"), a_native)?;
+//! let b_const = GVar::new_constant(ark_relations::ns!(cs, "b_as_constant"), b_native)?;
+//!
+//! // This returns the identity.
+//! let zero = GVar::zero();
+//!
+//! // Sanity check one + one = two
+//! let two_a = &a + &a + &zero;
+//! two_a.enforce_equal(&a.double()?)?;
+//!
+//! assert!(cs.is_satisfied()?);
+//!
+//! // Check that the value of &a + &b is correct.
+//! assert_eq!((&a + &b).value()?, a_native + &b_native);
+//!
+//! // Check that operations on variables and constants are equivalent.
+//! (&a + &b).enforce_equal(&(&a_const + &b_const))?;
+//! assert!(cs.is_satisfied()?);
+//! # Ok(())
+//! # }
+//! ```
+
+mod curves;
+mod fields;
+
+pub use curves::*;
+pub use fields::*;

grumpkin/src/curves/mod.rs

@@ -0,0 +1,54 @@
+// The parameters for the curve have been taken from
+// https://github.com/AztecProtocol/barretenberg/blob/97ccf76c42db581a8b8f8bfbcffe8ca015a3dd22/cpp/src/barretenberg/ecc/curves/grumpkin/grumpkin.hpp
+
+use crate::{fq::Fq, fr::Fr};
+use ark_ec::{
+    models::CurveConfig,
+    short_weierstrass::{self as sw, SWCurveConfig},
+};
+use ark_ff::{AdditiveGroup, Field, MontFp, Zero};
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Copy, Clone, Default, PartialEq, Eq)]
+pub struct GrumpkinConfig;
+
+impl CurveConfig for GrumpkinConfig {
+    type BaseField = Fq;
+    type ScalarField = Fr;
+
+    /// COFACTOR = 1
+    const COFACTOR: &'static [u64] = &[0x1];
+
+    /// COFACTOR_INV = 1
+    const COFACTOR_INV: Fr = Fr::ONE;
+}
+
+pub type Affine = sw::Affine<GrumpkinConfig>;
+pub type Projective = sw::Projective<GrumpkinConfig>;
+
+impl SWCurveConfig for GrumpkinConfig {
+    /// COEFF_A = 0
+    const COEFF_A: Fq = Fq::ZERO;
+
+    /// COEFF_B = -17
+    const COEFF_B: Fq = MontFp!("-17");
+
+    /// AFFINE_GENERATOR_COEFFS = (G1_GENERATOR_X, G1_GENERATOR_Y)
+    const GENERATOR: Affine = Affine::new_unchecked(G_GENERATOR_X, G_GENERATOR_Y);
+
+    #[inline(always)]
+    fn mul_by_a(_: Self::BaseField) -> Self::BaseField {
+        Self::BaseField::zero()
+    }
+}
+
+/// G_GENERATOR_X = 1
+/// Encoded in Montgomery form, so the value here is R mod p.
+pub const G_GENERATOR_X: Fq = MontFp!("1");
+
+/// G_GENERATOR_Y = sqrt(-16)
+/// Encoded in Montgomery form, so the value here is 2R mod p.
+pub const G_GENERATOR_Y: Fq =
+    MontFp!("17631683881184975370165255887551781615748388533673675138860");

grumpkin/src/curves/tests.rs

@@ -0,0 +1,4 @@
+use crate::Projective;
+use ark_algebra_test_templates::*;
+
+test_group!(g1; Projective; sw);

grumpkin/src/fields/fq.rs

@@ -0,0 +1 @@
+pub use ark_bn254::{Fr as Fq, FrConfig as FqConfig};

grumpkin/src/fields/fr.rs

@@ -0,0 +1 @@
+pub use ark_bn254::{Fq as Fr, FqConfig as FrConfig};

grumpkin/src/fields/mod.rs

@@ -0,0 +1,8 @@
+pub mod fq;
+pub use self::fq::*;
+
+pub mod fr;
+pub use self::fr::*;
+
+#[cfg(test)]
+mod tests;

grumpkin/src/fields/tests.rs

@@ -0,0 +1,5 @@
+use crate::{Fq, Fr};
+use ark_algebra_test_templates::*;
+
+test_field!(fr; Fr; mont_prime_field);
+test_field!(fq; Fq; mont_prime_field);

grumpkin/src/lib.rs

@@ -0,0 +1,33 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+#![deny(
+    warnings,
+    unused,
+    future_incompatible,
+    nonstandard_style,
+    rust_2018_idioms
+)]
+#![forbid(unsafe_code)]
+
+//! This library implements the prime-order curve Grumpkin, generated by
+//! Zachary J. Williamson from Aztec protocol. The main feature of this
+//! curve is that it forms a cycle with bn254, i.e. its scalar field and base
+//! field respectively are the base field and scalar field of bn254.
+//!
+//!
+//! Curve information:
+//! Grumpkin:
+//! * Base field: q =
+//!   21888242871839275222246405745257275088548364400416034343698204186575808495617
+//! * Scalar field: r =
+//!   21888242871839275222246405745257275088696311157297823662689037894645226208583
+//! * Curve equation: y^2 = x^3 - 17
+//! * Valuation(q - 1, 2) = 28
+//! * Valuation(r - 1, 2) = 1
+
+#[cfg(feature = "r1cs")]
+pub mod constraints;
+mod curves;
+mod fields;
+
+pub use curves::*;
+pub use fields::*;