feat: solve fixed_base_scalar_mul black box functions in rust (#3153)

acvm-repo/acir_field/src/generic_ark.rs

@@ -248,6 +248,10 @@ impl<F: PrimeField> FieldElement<F> {
         self.0.inverse_in_place().map(|f| FieldElement(*f))
     }
 
+    pub fn from_repr(field: F) -> Self {
+        Self(field)
+    }
+
     // XXX: This method is used while this field element
     // implementation is not generic.
     pub fn into_repr(self) -> F {

acvm-repo/acvm/src/pwg/blackbox/fixed_base_scalar_mul.rs

@@ -2,11 +2,9 @@ use acir::{
     circuit::opcodes::FunctionInput,
     native_types::{Witness, WitnessMap},
 };
+use acvm_blackbox_solver::BlackBoxFunctionSolver;
 
-use crate::{
-    pwg::{insert_value, witness_to_value, OpcodeResolutionError},
-    BlackBoxFunctionSolver,
-};
+use crate::pwg::{insert_value, witness_to_value, OpcodeResolutionError};
 
 pub(super) fn fixed_base_scalar_mul(
     backend: &impl BlackBoxFunctionSolver,

acvm-repo/barretenberg_blackbox_solver/Cargo.toml

@@ -16,15 +16,19 @@ repository.workspace = true
 acir.workspace = true
 acvm_blackbox_solver.workspace = true
 thiserror.workspace = true
-hex.workspace = true
-num-bigint.workspace = true
 
 rust-embed = { version = "6.6.0", features = [
     "debug-embed",
     "interpolate-folder-path",
     "include-exclude",
 ] }
 
+# BN254 fixed base scalar multiplication solver
+grumpkin = { git = "https://github.com/noir-lang/grumpkin", rev = "56d99799381f79e42148aaef0de2b0cf9a4b9a5d", features = ["std"] }
+ark-ec = { version = "^0.4.0", default-features = false }
+ark-ff = { version = "^0.4.0", default-features = false }
+num-bigint.workspace = true
+
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 wasmer = { version = "3.3", default-features = false, features = [
     "js-default",

acvm-repo/barretenberg_blackbox_solver/src/fixed_base_scalar_mul.rs

@@ -0,0 +1,115 @@
+use ark_ec::AffineRepr;
+use ark_ff::MontConfig;
+use num_bigint::BigUint;
+
+use acir::{BlackBoxFunc, FieldElement};
+
+use crate::BlackBoxResolutionError;
+
+pub fn fixed_base_scalar_mul(
+    low: &FieldElement,
+    high: &FieldElement,
+) -> Result<(FieldElement, FieldElement), BlackBoxResolutionError> {
+    let low: u128 = low.try_into_u128().ok_or_else(|| {
+        BlackBoxResolutionError::Failed(
+            BlackBoxFunc::FixedBaseScalarMul,
+            format!("Limb {} is not less than 2^128", low.to_hex()),
+        )
+    })?;
+
+    let high: u128 = high.try_into_u128().ok_or_else(|| {
+        BlackBoxResolutionError::Failed(
+            BlackBoxFunc::FixedBaseScalarMul,
+            format!("Limb {} is not less than 2^128", high.to_hex()),
+        )
+    })?;
+
+    let mut bytes = high.to_be_bytes().to_vec();
+    bytes.extend_from_slice(&low.to_be_bytes());
+
+    // Check if this is smaller than the grumpkin modulus
+    let grumpkin_integer = BigUint::from_bytes_be(&bytes);
+
+    if grumpkin_integer >= grumpkin::FrConfig::MODULUS.into() {
+        return Err(BlackBoxResolutionError::Failed(
+            BlackBoxFunc::FixedBaseScalarMul,
+            format!("{} is not a valid grumpkin scalar", grumpkin_integer.to_str_radix(16)),
+        ));
+    }
+
+    let result = grumpkin::SWAffine::from(
+        grumpkin::SWAffine::generator().mul_bigint(grumpkin_integer.to_u64_digits()),
+    );
+    if let Some((res_x, res_y)) = result.xy() {
+        Ok((FieldElement::from_repr(*res_x), FieldElement::from_repr(*res_y)))
+    } else {
+        Ok((FieldElement::zero(), FieldElement::zero()))
+    }
+}
+
+#[cfg(test)]
+mod grumpkin_fixed_base_scalar_mul {
+    use ark_ff::BigInteger;
+
+    use super::*;
+    #[test]
+    fn smoke_test() -> Result<(), BlackBoxResolutionError> {
+        let input = FieldElement::one();
+
+        let res = fixed_base_scalar_mul(&input, &FieldElement::zero())?;
+        let x = "0000000000000000000000000000000000000000000000000000000000000001";
+        let y = "0000000000000002cf135e7506a45d632d270d45f1181294833fc48d823f272c";
+
+        assert_eq!(x, res.0.to_hex());
+        assert_eq!(y, res.1.to_hex());
+        Ok(())
+    }
+    #[test]
+    fn low_high_smoke_test() -> Result<(), BlackBoxResolutionError> {
+        let low = FieldElement::one();
+        let high = FieldElement::from(2u128);
+
+        let res = fixed_base_scalar_mul(&low, &high)?;
+        let x = "0702ab9c7038eeecc179b4f209991bcb68c7cb05bf4c532d804ccac36199c9a9";
+        let y = "23f10e9e43a3ae8d75d24154e796aae12ae7af546716e8f81a2564f1b5814130";
+
+        assert_eq!(x, res.0.to_hex());
+        assert_eq!(y, res.1.to_hex());
+        Ok(())
+    }
+
+    #[test]
+    fn rejects_invalid_limbs() {
+        let max_limb = FieldElement::from(u128::MAX);
+        let invalid_limb = max_limb + FieldElement::one();
+
+        let expected_error =  Err(BlackBoxResolutionError::Failed(
+            BlackBoxFunc::FixedBaseScalarMul,
+            "Limb 0000000000000000000000000000000100000000000000000000000000000000 is not less than 2^128".into()
+        ));
+
+        let res = fixed_base_scalar_mul(&invalid_limb, &FieldElement::zero());
+        assert_eq!(res, expected_error);
+
+        let res = fixed_base_scalar_mul(&FieldElement::zero(), &invalid_limb);
+        assert_eq!(res, expected_error);
+    }
+
+    #[test]
+    fn rejects_grumpkin_modulus() {
+        let x = grumpkin::FrConfig::MODULUS.to_bytes_be();
+
+        let high = FieldElement::from_be_bytes_reduce(&x[0..16]);
+        let low = FieldElement::from_be_bytes_reduce(&x[16..32]);
+
+        let res = fixed_base_scalar_mul(&low, &high);
+
+        assert_eq!(
+            res,
+            Err(BlackBoxResolutionError::Failed(
+                BlackBoxFunc::FixedBaseScalarMul,
+                "30644e72e131a029b85045b68181585d97816a916871ca8d3c208c16d87cfd47 is not a valid grumpkin scalar".into()
+            ))
+        );
+    }
+}

acvm-repo/barretenberg_blackbox_solver/src/lib.rs

@@ -5,11 +5,13 @@
 use acir::{BlackBoxFunc, FieldElement};
 use acvm_blackbox_solver::{BlackBoxFunctionSolver, BlackBoxResolutionError};
 
+mod fixed_base_scalar_mul;
 mod wasm;
 
+pub use fixed_base_scalar_mul::fixed_base_scalar_mul;
 use wasm::Barretenberg;
 
-use self::wasm::{Pedersen, ScalarMul, SchnorrSig};
+use self::wasm::{Pedersen, SchnorrSig};
 
 #[deprecated = "The `BarretenbergSolver` is a temporary solution and will be removed in future."]
 pub struct BarretenbergSolver {
@@ -77,9 +79,6 @@ impl BlackBoxFunctionSolver for BarretenbergSolver {
         low: &FieldElement,
         high: &FieldElement,
     ) -> Result<(FieldElement, FieldElement), BlackBoxResolutionError> {
-        #[allow(deprecated)]
-        self.blackbox_vendor.fixed_base(low, high).map_err(|err| {
-            BlackBoxResolutionError::Failed(BlackBoxFunc::FixedBaseScalarMul, err.to_string())
-        })
+        fixed_base_scalar_mul(low, high)
     }
 }

acvm-repo/barretenberg_blackbox_solver/src/wasm/mod.rs

@@ -6,13 +6,11 @@
 
 mod barretenberg_structures;
 mod pedersen;
-mod scalar_mul;
 mod schnorr;
 
 use barretenberg_structures::Assignments;
 
 pub(crate) use pedersen::Pedersen;
-pub(crate) use scalar_mul::ScalarMul;
 pub(crate) use schnorr::SchnorrSig;
 
 /// The number of bytes necessary to store a `FieldElement`.
@@ -34,10 +32,6 @@ pub(crate) enum FeatureError {
     NoValue,
     #[error("Value expected to be i32")]
     InvalidI32,
-    #[error("Value {scalar_as_hex} is not a valid grumpkin scalar")]
-    InvalidGrumpkinScalar { scalar_as_hex: String },
-    #[error("Limb {limb_as_hex} is not less than 2^128")]
-    InvalidGrumpkinScalarLimb { limb_as_hex: String },
     #[error("Could not convert value {value} from i32 to u32")]
     InvalidU32 { value: i32, source: std::num::TryFromIntError },
     #[error("Could not convert value {value} from i32 to usize")]

acvm-repo/blackbox_solver/Cargo.toml

@@ -34,6 +34,7 @@ p256 = { version = "0.11.0", features = [
     "arithmetic",
 ] }
 
+
 [features]
 default = ["bn254"]
 bn254 = ["acir/bn254"]

cspell.json

@@ -49,6 +49,7 @@
         "fxhash",
         "getrandom",
         "gloo",
+        "grumpkin",
         "Guillaume",
         "hasher",
         "hexdigit",

deny.toml

@@ -99,4 +99,7 @@ unknown-registry = "warn"
 # Lint level for what to happen when a crate from a git repository that is not
 # in the allow list is encountered
 unknown-git = "deny"
-allow-git = ["https://github.com/jfecher/chumsky"]
+allow-git = [
+    "https://github.com/noir-lang/grumpkin",
+    "https://github.com/jfecher/chumsky"
+]