Adds Bowe-Hopwood hash

crypto-primitives/src/crh/bowe_hopwood/constraints.rs

@@ -0,0 +1,206 @@
+use algebra::Field;
+use std::hash::Hash;
+
+use crate::crh::{
+    bowe_hopwood::{BoweHopwoodPedersenCRH, BoweHopwoodPedersenParameters, CHUNK_SIZE},
+    pedersen::PedersenWindow,
+    FixedLengthCRHGadget,
+};
+use algebra::groups::Group;
+use r1cs_core::{ConstraintSystem, SynthesisError};
+use r1cs_std::{alloc::AllocGadget, groups::GroupGadget, uint8::UInt8};
+
+use r1cs_std::bits::boolean::Boolean;
+use std::{borrow::Borrow, marker::PhantomData};
+
+#[derive(Derivative)]
+#[derivative(Clone(
+    bound = "G: Group, W: PedersenWindow, ConstraintF: Field, GG: GroupGadget<G, ConstraintF>"
+))]
+pub struct BoweHopwoodPedersenCRHGadgetParameters<
+    G: Group,
+    W: PedersenWindow,
+    ConstraintF: Field,
+    GG: GroupGadget<G, ConstraintF>,
+> {
+    params:   BoweHopwoodPedersenParameters<G>,
+    _group_g: PhantomData<GG>,
+    _engine:  PhantomData<ConstraintF>,
+    _window:  PhantomData<W>,
+}
+
+pub struct BoweHopwoodPedersenCRHGadget<
+    G: Group,
+    ConstraintF: Field,
+    GG: GroupGadget<G, ConstraintF>,
+> {
+    _group:        PhantomData<*const G>,
+    _group_gadget: PhantomData<*const GG>,
+    _engine:       PhantomData<ConstraintF>,
+}
+
+impl<ConstraintF, G, GG, W> FixedLengthCRHGadget<BoweHopwoodPedersenCRH<G, W>, ConstraintF>
+    for BoweHopwoodPedersenCRHGadget<G, ConstraintF, GG>
+where
+    ConstraintF: Field,
+    G: Group + Hash,
+    GG: GroupGadget<G, ConstraintF>,
+    W: PedersenWindow,
+{
+    type OutputGadget = GG;
+    type ParametersGadget = BoweHopwoodPedersenCRHGadgetParameters<G, W, ConstraintF, GG>;
+
+    fn check_evaluation_gadget<CS: ConstraintSystem<ConstraintF>>(
+        cs: CS,
+        parameters: &Self::ParametersGadget,
+        input: &[UInt8],
+    ) -> Result<Self::OutputGadget, SynthesisError> {
+        // Pad the input if it is not the current length.
+        let mut input_in_bits: Vec<_> = input.iter().flat_map(|byte| byte.into_bits_le()).collect();
+        if (input_in_bits.len()) % CHUNK_SIZE != 0 {
+            let current_length = input_in_bits.len();
+            for _ in 0..(CHUNK_SIZE - current_length % CHUNK_SIZE) {
+                input_in_bits.push(Boolean::constant(false));
+            }
+        }
+        assert!(input_in_bits.len() % CHUNK_SIZE == 0);
+        assert_eq!(parameters.params.generators.len(), W::NUM_WINDOWS);
+        for generators in parameters.params.generators.iter() {
+            assert_eq!(generators.len(), W::WINDOW_SIZE);
+        }
+
+        // Allocate new variable for the result.
+        let input_in_bits = input_in_bits
+            .chunks(W::WINDOW_SIZE * CHUNK_SIZE)
+            .map(|x| x.chunks(CHUNK_SIZE).into_iter().collect::<Vec<_>>())
+            .collect::<Vec<_>>();
+        let result = GG::precomputed_base_3_bit_signed_digit_scalar_mul(
+            cs,
+            &parameters.params.generators,
+            &input_in_bits,
+        )?;
+
+        Ok(result)
+    }
+}
+
+impl<G: Group, W: PedersenWindow, ConstraintF: Field, GG: GroupGadget<G, ConstraintF>>
+    AllocGadget<BoweHopwoodPedersenParameters<G>, ConstraintF>
+    for BoweHopwoodPedersenCRHGadgetParameters<G, W, ConstraintF, GG>
+{
+    fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(
+        _cs: CS,
+        value_gen: F,
+    ) -> Result<Self, SynthesisError>
+    where
+        F: FnOnce() -> Result<T, SynthesisError>,
+        T: Borrow<BoweHopwoodPedersenParameters<G>>,
+    {
+        let params = value_gen()?.borrow().clone();
+        Ok(BoweHopwoodPedersenCRHGadgetParameters {
+            params,
+            _group_g: PhantomData,
+            _engine: PhantomData,
+            _window: PhantomData,
+        })
+    }
+
+    fn alloc_input<F, T, CS: ConstraintSystem<ConstraintF>>(
+        _cs: CS,
+        value_gen: F,
+    ) -> Result<Self, SynthesisError>
+    where
+        F: FnOnce() -> Result<T, SynthesisError>,
+        T: Borrow<BoweHopwoodPedersenParameters<G>>,
+    {
+        let params = value_gen()?.borrow().clone();
+        Ok(BoweHopwoodPedersenCRHGadgetParameters {
+            params,
+            _group_g: PhantomData,
+            _engine: PhantomData,
+            _window: PhantomData,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use algebra::fields::sw6::fr::Fr;
+    use rand::{thread_rng, Rng};
+
+    use crate::crh::{
+        bowe_hopwood::{constraints::BoweHopwoodPedersenCRHGadget, BoweHopwoodPedersenCRH},
+        pedersen::PedersenWindow,
+        FixedLengthCRH, FixedLengthCRHGadget,
+    };
+    use algebra::{curves::edwards_sw6::EdwardsProjective as Edwards, ProjectiveCurve};
+    use r1cs_core::ConstraintSystem;
+    use r1cs_std::{
+        alloc::AllocGadget, groups::curves::twisted_edwards::edwards_sw6::EdwardsSWGadget,
+        test_constraint_system::TestConstraintSystem, uint8::UInt8,
+    };
+
+    type TestCRH = BoweHopwoodPedersenCRH<Edwards, Window>;
+    type TestCRHGadget = BoweHopwoodPedersenCRHGadget<Edwards, Fr, EdwardsSWGadget>;
+
+    #[derive(Clone, PartialEq, Eq, Hash)]
+    pub(super) struct Window;
+
+    impl PedersenWindow for Window {
+        const WINDOW_SIZE: usize = 90;
+        const NUM_WINDOWS: usize = 8;
+    }
+
+    fn generate_input<CS: ConstraintSystem<Fr>, R: Rng>(
+        mut cs: CS,
+        rng: &mut R,
+    ) -> ([u8; 270], Vec<UInt8>) {
+        let mut input = [1u8; 270];
+        rng.fill_bytes(&mut input);
+
+        let mut input_bytes = vec![];
+        for (byte_i, input_byte) in input.into_iter().enumerate() {
+            let cs = cs.ns(|| format!("input_byte_gadget_{}", byte_i));
+            input_bytes.push(UInt8::alloc(cs, || Ok(*input_byte)).unwrap());
+        }
+        (input, input_bytes)
+    }
+
+    #[test]
+    fn crh_primitive_gadget_test() {
+        let rng = &mut thread_rng();
+        let mut cs = TestConstraintSystem::<Fr>::new();
+
+        let (input, input_bytes) = generate_input(&mut cs, rng);
+        println!("number of constraints for input: {}", cs.num_constraints());
+
+        let parameters = TestCRH::setup(rng).unwrap();
+        let primitive_result = TestCRH::evaluate(&parameters, &input).unwrap();
+
+        let gadget_parameters =
+            <TestCRHGadget as FixedLengthCRHGadget<TestCRH, Fr>>::ParametersGadget::alloc(
+                &mut cs.ns(|| "gadget_parameters"),
+                || Ok(&parameters),
+            )
+            .unwrap();
+        println!(
+            "number of constraints for input + params: {}",
+            cs.num_constraints()
+        );
+
+        let gadget_result =
+            <TestCRHGadget as FixedLengthCRHGadget<TestCRH, Fr>>::check_evaluation_gadget(
+                &mut cs.ns(|| "gadget_evaluation"),
+                &gadget_parameters,
+                &input_bytes,
+            )
+            .unwrap();
+
+        println!("number of constraints total: {}", cs.num_constraints());
+
+        let primitive_result = primitive_result.into_affine();
+        assert_eq!(primitive_result.x, gadget_result.x.value.unwrap());
+        assert_eq!(primitive_result.y, gadget_result.y.value.unwrap());
+        assert!(cs.is_satisfied());
+    }
+}

crypto-primitives/src/crh/bowe_hopwood/mod.rs

@@ -0,0 +1,194 @@
+use crate::Error;
+use rand::Rng;
+use rayon::prelude::*;
+use std::{
+    fmt::{Debug, Formatter, Result as FmtResult},
+    marker::PhantomData,
+};
+
+use super::pedersen::{bytes_to_bits, PedersenCRH, PedersenWindow};
+use crate::crh::FixedLengthCRH;
+use algebra::{biginteger::BigInteger, fields::PrimeField, groups::Group};
+
+#[cfg(feature = "r1cs")]
+pub mod constraints;
+
+pub const CHUNK_SIZE: usize = 3;
+
+#[derive(Clone, Default)]
+pub struct BoweHopwoodPedersenParameters<G: Group> {
+    pub generators: Vec<Vec<G>>,
+}
+
+pub struct BoweHopwoodPedersenCRH<G: Group, W: PedersenWindow> {
+    group:  PhantomData<G>,
+    window: PhantomData<W>,
+}
+
+impl<G: Group, W: PedersenWindow> BoweHopwoodPedersenCRH<G, W> {
+    pub fn create_generators<R: Rng>(rng: &mut R) -> Vec<Vec<G>> {
+        let mut generators = Vec::new();
+        for _ in 0..W::NUM_WINDOWS {
+            let mut generators_for_segment = Vec::new();
+            let mut base = G::rand(rng);
+            for _ in 0..W::WINDOW_SIZE {
+                generators_for_segment.push(base);
+                for _ in 0..4 {
+                    base.double_in_place();
+                }
+            }
+            generators.push(generators_for_segment);
+        }
+        generators
+    }
+}
+
+impl<G: Group, W: PedersenWindow> FixedLengthCRH for BoweHopwoodPedersenCRH<G, W> {
+    const INPUT_SIZE_BITS: usize = PedersenCRH::<G, W>::INPUT_SIZE_BITS;
+    type Output = G;
+    type Parameters = BoweHopwoodPedersenParameters<G>;
+
+    fn setup<R: Rng>(rng: &mut R) -> Result<Self::Parameters, Error> {
+        fn calculate_num_chunks_in_segment<F: PrimeField>() -> usize {
+            let upper_limit = F::modulus_minus_one_div_two();
+            let mut c = 0;
+            let mut range = F::BigInt::from(2_u64);
+            while range < upper_limit {
+                range.muln(4);
+                c += 1;
+            }
+
+            c
+        }
+
+        let maximum_num_chunks_in_segment = calculate_num_chunks_in_segment::<G::ScalarField>();
+        if W::WINDOW_SIZE > maximum_num_chunks_in_segment {
+            return Err(format!(
+                "Bowe-Hopwood hash must have a window size resulting in scalars < (p-1)/2, \
+                 maximum segment size is {}",
+                maximum_num_chunks_in_segment
+            )
+            .into());
+        }
+
+        let time = start_timer!(|| format!(
+            "BoweHopwoodPedersenCRH::Setup: {} segments of {} 3-bit chunks; {{0,1}}^{{{}}} -> G",
+            W::NUM_WINDOWS,
+            W::WINDOW_SIZE,
+            W::WINDOW_SIZE * W::NUM_WINDOWS * CHUNK_SIZE
+        ));
+        let generators = Self::create_generators(rng);
+        end_timer!(time);
+        Ok(Self::Parameters { generators })
+    }
+
+    fn evaluate(parameters: &Self::Parameters, input: &[u8]) -> Result<Self::Output, Error> {
+        let eval_time = start_timer!(|| "BoweHopwoodPedersenCRH::Eval");
+
+        if (input.len() * 8) > W::WINDOW_SIZE * W::NUM_WINDOWS * CHUNK_SIZE {
+            panic!(
+                "incorrect input length {:?} for window params {:?}x{:?}x{}",
+                input.len(),
+                W::WINDOW_SIZE,
+                W::NUM_WINDOWS,
+                CHUNK_SIZE,
+            );
+        }
+
+        let mut padded_input = Vec::with_capacity(input.len());
+        let input = bytes_to_bits(input);
+        // Pad the input if it is not the current length.
+        padded_input.extend_from_slice(&input);
+        if input.len() % CHUNK_SIZE != 0 {
+            let current_length = input.len();
+            for _ in 0..(CHUNK_SIZE - current_length % CHUNK_SIZE) {
+                padded_input.push(false);
+            }
+        }
+
+        assert_eq!(padded_input.len() % CHUNK_SIZE, 0);
+
+        assert_eq!(
+            parameters.generators.len(),
+            W::NUM_WINDOWS,
+            "Incorrect pp of size {:?} for window params {:?}x{:?}x{}",
+            parameters.generators.len(),
+            W::WINDOW_SIZE,
+            W::NUM_WINDOWS,
+            CHUNK_SIZE,
+        );
+        for generators in parameters.generators.iter() {
+            assert_eq!(generators.len(), W::WINDOW_SIZE);
+        }
+        assert_eq!(CHUNK_SIZE, 3);
+
+        // Compute sum of h_i^{sum of (1-2*c_{i,j,2})*(1+c_{i,j,0}+2*c_{i,j,1})*2^{4*(j-1)} for all j in segment} for all i. 
+        // Described in section 5.4.1.7 in the Zcash protocol specification.
+        let result = padded_input
+            .par_chunks(W::WINDOW_SIZE * CHUNK_SIZE)
+            .zip(&parameters.generators)
+            .map(|(segment_bits, segment_generators)| {
+                segment_bits
+                    .par_chunks(CHUNK_SIZE)
+                    .zip(segment_generators)
+                    .map(|(chunk_bits, generator)| {
+                        let mut encoded = generator.clone();
+                        if chunk_bits[0] {
+                            encoded = encoded + &generator;
+                        }
+                        if chunk_bits[1] {
+                            encoded = encoded + &generator.double();
+                        }
+                        if chunk_bits[2] {
+                            encoded = encoded.neg();
+                        }
+                        encoded
+                    })
+                    .reduce(|| G::zero(), |a, b| a + &b)
+            })
+            .reduce(|| G::zero(), |a, b| a + &b);
+        end_timer!(eval_time);
+
+        Ok(result)
+    }
+}
+
+impl<G: Group> Debug for BoweHopwoodPedersenParameters<G> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, "Bowe-Hopwood Pedersen Hash Parameters {{\n")?;
+        for (i, g) in self.generators.iter().enumerate() {
+            write!(f, "\t  Generator {}: {:?}\n", i, g)?;
+        }
+        write!(f, "}}\n")
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{
+        crh::{bowe_hopwood::BoweHopwoodPedersenCRH, pedersen::PedersenWindow},
+        FixedLengthCRH,
+    };
+    use algebra::curves::edwards_sw6::EdwardsProjective;
+    use rand::thread_rng;
+
+    #[test]
+    fn test_simple_bh() {
+        #[derive(Clone)]
+        struct TestWindow {}
+        impl PedersenWindow for TestWindow {
+            const WINDOW_SIZE: usize = 90;
+            const NUM_WINDOWS: usize = 8;
+        }
+
+        let rng = &mut thread_rng();
+        let params =
+            <BoweHopwoodPedersenCRH<EdwardsProjective, TestWindow> as FixedLengthCRH>::setup(rng)
+                .unwrap();
+        <BoweHopwoodPedersenCRH<EdwardsProjective, TestWindow> as FixedLengthCRH>::evaluate(
+            &params,
+            &[1, 2, 3],
+        )
+        .unwrap();
+    }
+}

crypto-primitives/src/crh/mod.rs

@@ -2,6 +2,7 @@ use algebra::bytes::ToBytes;
 use rand::Rng;
 use std::hash::Hash;
 
+pub mod bowe_hopwood;
 pub mod injective_map;
 pub mod pedersen;
 

crypto-primitives/src/nizk/groth16/constraints.rs

@@ -62,7 +62,7 @@ impl
             alpha_g1_beta_g2,
             gamma_g2_neg_pc,
             delta_g2_neg_pc,
-            gamma_abc_g1:     self.gamma_abc_g1.clone(),
+            gamma_abc_g1: self.gamma_abc_g1.clone(),
         })
     }
 }

r1cs-std/src/alloc.rs

@@ -12,7 +12,10 @@ where
         F: FnOnce() -> Result<T, SynthesisError>,
         T: Borrow<V>;
 
-    fn alloc_checked<F, T, CS: ConstraintSystem<ConstraintF>>(cs: CS, f: F) -> Result<Self, SynthesisError>
+    fn alloc_checked<F, T, CS: ConstraintSystem<ConstraintF>>(
+        cs: CS,
+        f: F,
+    ) -> Result<Self, SynthesisError>
     where
         F: FnOnce() -> Result<T, SynthesisError>,
         T: Borrow<V>,
@@ -20,7 +23,10 @@ where
         Self::alloc(cs, f)
     }
 
-    fn alloc_input<F, T, CS: ConstraintSystem<ConstraintF>>(cs: CS, f: F) -> Result<Self, SynthesisError>
+    fn alloc_input<F, T, CS: ConstraintSystem<ConstraintF>>(
+        cs: CS,
+        f: F,
+    ) -> Result<Self, SynthesisError>
     where
         F: FnOnce() -> Result<T, SynthesisError>,
         T: Borrow<V>;
@@ -37,8 +43,13 @@ where
     }
 }
 
-impl<I, ConstraintF: Field, A: AllocGadget<I, ConstraintF>> AllocGadget<[I], ConstraintF> for Vec<A> {
-    fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(mut cs: CS, f: F) -> Result<Self, SynthesisError>
+impl<I, ConstraintF: Field, A: AllocGadget<I, ConstraintF>> AllocGadget<[I], ConstraintF>
+    for Vec<A>
+{
+    fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(
+        mut cs: CS,
+        f: F,
+    ) -> Result<Self, SynthesisError>
     where
         F: FnOnce() -> Result<T, SynthesisError>,
         T: Borrow<[I]>,
@@ -52,7 +63,10 @@ impl> AllocGadget<[I], Con
         Ok(vec)
     }
 
-    fn alloc_input<F, T, CS: ConstraintSystem<ConstraintF>>(mut cs: CS, f: F) -> Result<Self, SynthesisError>
+    fn alloc_input<F, T, CS: ConstraintSystem<ConstraintF>>(
+        mut cs: CS,
+        f: F,
+    ) -> Result<Self, SynthesisError>
     where
         F: FnOnce() -> Result<T, SynthesisError>,
         T: Borrow<[I]>,

r1cs-std/src/bits/boolean.rs

@@ -1,7 +1,6 @@
 use algebra::{BitIterator, Field, FpParameters, PrimeField};
 
-use crate::prelude::*;
-use crate::Assignment;
+use crate::{prelude::*, Assignment};
 use r1cs_core::{ConstraintSystem, LinearCombination, SynthesisError, Variable};
 use std::borrow::Borrow;
 
@@ -346,7 +345,11 @@ impl Boolean {
         }
     }
 
-    pub fn lc<ConstraintF: Field>(&self, one: Variable, coeff: ConstraintF) -> LinearCombination<ConstraintF> {
+    pub fn lc<ConstraintF: Field>(
+        &self,
+        one: Variable,
+        coeff: ConstraintF,
+    ) -> LinearCombination<ConstraintF> {
         match *self {
             Boolean::Constant(c) => {
                 if c {
@@ -396,7 +399,11 @@ impl Boolean {
     }
 
     /// Perform XOR over two boolean operands
-    pub fn xor<'a, ConstraintF, CS>(cs: CS, a: &'a Self, b: &'a Self) -> Result<Self, SynthesisError>
+    pub fn xor<'a, ConstraintF, CS>(
+        cs: CS,
+        a: &'a Self,
+        b: &'a Self,
+    ) -> Result<Self, SynthesisError>
     where
         ConstraintF: Field,
         CS: ConstraintSystem<ConstraintF>,
@@ -441,7 +448,11 @@ impl Boolean {
     }
 
     /// Perform AND over two boolean operands
-    pub fn and<'a, ConstraintF, CS>(cs: CS, a: &'a Self, b: &'a Self) -> Result<Self, SynthesisError>
+    pub fn and<'a, ConstraintF, CS>(
+        cs: CS,
+        a: &'a Self,
+        b: &'a Self,
+    ) -> Result<Self, SynthesisError>
     where
         ConstraintF: Field,
         CS: ConstraintSystem<ConstraintF>,
@@ -629,7 +640,10 @@ impl From for Boolean {
 }
 
 impl<ConstraintF: Field> AllocGadget<bool, ConstraintF> for Boolean {
-    fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(cs: CS, value_gen: F) -> Result<Self, SynthesisError>
+    fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(
+        cs: CS,
+        value_gen: F,
+    ) -> Result<Self, SynthesisError>
     where
         F: FnOnce() -> Result<T, SynthesisError>,
         T: Borrow<bool>,
@@ -713,7 +727,10 @@ impl ConditionalEqGadget for Boolean {
 }
 
 impl<ConstraintF: Field> ToBytesGadget<ConstraintF> for Boolean {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut bits = vec![Boolean::constant(false); 7];
         bits.push(*self);
         bits.reverse();
@@ -734,15 +751,11 @@ impl ToBytesGadget for Boolean {
 #[cfg(test)]
 mod test {
     use super::{AllocatedBit, Boolean};
-    use crate::{
-        test_constraint_system::TestConstraintSystem,
-        prelude::*
-    };
-    use algebra::{fields::bls12_381::Fr, BitIterator, Field, PrimeField};
-    use algebra::UniformRand;
-use rand::SeedableRng;
-use rand_xorshift::XorShiftRng;
+    use crate::{prelude::*, test_constraint_system::TestConstraintSystem};
+    use algebra::{fields::bls12_381::Fr, BitIterator, Field, PrimeField, UniformRand};
     use r1cs_core::ConstraintSystem;
+    use rand::SeedableRng;
+    use rand_xorshift::XorShiftRng;
     use std::str::FromStr;
 
     #[test]
@@ -1775,8 +1788,8 @@ use rand_xorshift::XorShiftRng;
         //     let mut bits = vec![];
         //     for (i, b) in BitIterator::new(r).skip(1).enumerate() {
         //         bits.push(Boolean::from(
-        //             AllocatedBit::alloc(cs.ns(|| format!("bit_gadget {}", i)),
-        // Some(b))                 .unwrap(),
+        //             AllocatedBit::alloc(cs.ns(|| format!("bit_gadget {}",
+        // i)), Some(b))                 .unwrap(),
         //         ));
         //     }
 

r1cs-std/src/bits/mod.rs

@@ -7,7 +7,10 @@ pub mod uint32;
 pub mod uint8;
 
 pub trait ToBitsGadget<ConstraintF: Field> {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, cs: CS) -> Result<Vec<Boolean>, SynthesisError>;
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError>;
 
     /// Additionally checks if the produced list of booleans is 'valid'.
     fn to_bits_strict<CS: ConstraintSystem<ConstraintF>>(
@@ -17,7 +20,10 @@ pub trait ToBitsGadget {
 }
 
 impl<ConstraintF: Field> ToBitsGadget<ConstraintF> for Boolean {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, _: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         Ok(vec![self.clone()])
     }
 
@@ -30,7 +36,10 @@ impl ToBitsGadget for Boolean {
 }
 
 impl<ConstraintF: Field> ToBitsGadget<ConstraintF> for [Boolean] {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         Ok(self.to_vec())
     }
 
@@ -42,7 +51,10 @@ impl ToBitsGadget for [Boolean] {
     }
 }
 impl<ConstraintF: Field> ToBitsGadget<ConstraintF> for Vec<Boolean> {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         Ok(self.clone())
     }
 
@@ -55,7 +67,10 @@ impl ToBitsGadget for Vec {
 }
 
 impl<ConstraintF: Field> ToBitsGadget<ConstraintF> for [UInt8] {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         let mut result = Vec::with_capacity(&self.len() * 8);
         for byte in self {
             result.extend_from_slice(&byte.into_bits_le());
@@ -72,7 +87,10 @@ impl ToBitsGadget for [UInt8] {
 }
 
 pub trait ToBytesGadget<ConstraintF: Field> {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, cs: CS) -> Result<Vec<UInt8>, SynthesisError>;
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError>;
 
     /// Additionally checks if the produced list of booleans is 'valid'.
     fn to_bytes_strict<CS: ConstraintSystem<ConstraintF>>(
@@ -82,7 +100,10 @@ pub trait ToBytesGadget {
 }
 
 impl<ConstraintF: Field> ToBytesGadget<ConstraintF> for [UInt8] {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         Ok(self.to_vec())
     }
 
@@ -94,8 +115,13 @@ impl ToBytesGadget for [UInt8] {
     }
 }
 
-impl<'a, ConstraintF: Field, T: 'a + ToBytesGadget<ConstraintF>> ToBytesGadget<ConstraintF> for &'a T {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+impl<'a, ConstraintF: Field, T: 'a + ToBytesGadget<ConstraintF>> ToBytesGadget<ConstraintF>
+    for &'a T
+{
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         (*self).to_bytes(cs)
     }
 
@@ -108,7 +134,10 @@ impl<'a, ConstraintF: Field, T: 'a + ToBytesGadget> ToBytesGadget
 }
 
 impl<'a, ConstraintF: Field> ToBytesGadget<ConstraintF> for &'a [UInt8] {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         Ok(self.to_vec())
     }
 

r1cs-std/src/bits/uint32.rs

@@ -1,10 +1,12 @@
-use algebra::{FpParameters, PrimeField, Field};
+use algebra::{Field, FpParameters, PrimeField};
 
 use r1cs_core::{ConstraintSystem, LinearCombination, SynthesisError};
 
-use crate::boolean::{AllocatedBit, Boolean};
-use crate::Assignment;
-use crate::prelude::*;
+use crate::{
+    boolean::{AllocatedBit, Boolean},
+    prelude::*,
+    Assignment,
+};
 
 /// Represents an interpretation of 32 `Boolean` objects as an
 /// unsigned integer.
@@ -270,7 +272,10 @@ impl UInt32 {
 
 impl<ConstraintF: Field> ToBytesGadget<ConstraintF> for UInt32 {
     #[inline]
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, _cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let value_chunks = match self.value.map(|val| {
             use algebra::bytes::ToBytes;
             let mut bytes = [0u8; 4];
@@ -340,9 +345,9 @@ mod test {
     use super::UInt32;
     use crate::{bits::boolean::Boolean, test_constraint_system::TestConstraintSystem};
     use algebra::fields::{bls12_381::Fr, Field};
+    use r1cs_core::ConstraintSystem;
     use rand::{Rng, SeedableRng};
     use rand_xorshift::XorShiftRng;
-    use r1cs_core::ConstraintSystem;
 
     #[test]
     fn test_uint32_from_bits() {

r1cs-std/src/bits/uint8.rs

@@ -1,11 +1,8 @@
-use algebra::{ToConstraintField, FpParameters, Field, PrimeField};
+use algebra::{Field, FpParameters, PrimeField, ToConstraintField};
 
 use r1cs_core::{ConstraintSystem, SynthesisError};
 
-use crate::boolean::AllocatedBit;
-use crate::fields::fp::FpGadget;
-use crate::prelude::*;
-use crate::Assignment;
+use crate::{boolean::AllocatedBit, fields::fp::FpGadget, prelude::*, Assignment};
 use std::borrow::Borrow;
 
 /// Represents an interpretation of 8 `Boolean` objects as an
@@ -53,7 +50,10 @@ impl UInt8 {
         }
     }
 
-    pub fn alloc_vec<ConstraintF, CS, T>(mut cs: CS, values: &[T]) -> Result<Vec<Self>, SynthesisError>
+    pub fn alloc_vec<ConstraintF, CS, T>(
+        mut cs: CS,
+        values: &[T],
+    ) -> Result<Vec<Self>, SynthesisError>
     where
         ConstraintF: Field,
         CS: ConstraintSystem<ConstraintF>,
@@ -69,15 +69,20 @@ impl UInt8 {
     }
 
     /// Allocates a vector of `u8`'s by first converting (chunks of) them to
-    /// `ConstraintF` elements, (thus reducing the number of input allocations), and
-    /// then converts this list of `ConstraintF` gadgets back into bytes.
-    pub fn alloc_input_vec<ConstraintF, CS>(mut cs: CS, values: &[u8]) -> Result<Vec<Self>, SynthesisError>
+    /// `ConstraintF` elements, (thus reducing the number of input allocations),
+    /// and then converts this list of `ConstraintF` gadgets back into
+    /// bytes.
+    pub fn alloc_input_vec<ConstraintF, CS>(
+        mut cs: CS,
+        values: &[u8],
+    ) -> Result<Vec<Self>, SynthesisError>
     where
         ConstraintF: PrimeField,
         CS: ConstraintSystem<ConstraintF>,
     {
         let values_len = values.len();
-        let field_elements: Vec<ConstraintF> = ToConstraintField::<ConstraintF>::to_field_elements(values).unwrap();
+        let field_elements: Vec<ConstraintF> =
+            ToConstraintField::<ConstraintF>::to_field_elements(values).unwrap();
 
         let max_size = 8 * (ConstraintF::Params::CAPACITY / 8) as usize;
         let mut allocated_bits = Vec::new();
@@ -294,9 +299,9 @@ mod test {
     use super::UInt8;
     use crate::{prelude::*, test_constraint_system::TestConstraintSystem};
     use algebra::fields::bls12_381::Fr;
+    use r1cs_core::ConstraintSystem;
     use rand::{Rng, SeedableRng};
     use rand_xorshift::XorShiftRng;
-    use r1cs_core::ConstraintSystem;
 
     #[test]
     fn test_uint8_from_bits_to_bits() {

r1cs-std/src/eq.rs

@@ -1,6 +1,6 @@
 use crate::prelude::*;
-use r1cs_core::{ConstraintSystem, SynthesisError};
 use algebra::Field;
+use r1cs_core::{ConstraintSystem, SynthesisError};
 
 /// If `condition == 1`, then enforces that `self` and `other` are equal;
 /// otherwise, it doesn't enforce anything.
@@ -14,7 +14,9 @@ pub trait ConditionalEqGadget: Eq {
 
     fn cost() -> usize;
 }
-impl<T: ConditionalEqGadget<ConstraintF>, ConstraintF: Field> ConditionalEqGadget<ConstraintF> for [T] {
+impl<T: ConditionalEqGadget<ConstraintF>, ConstraintF: Field> ConditionalEqGadget<ConstraintF>
+    for [T]
+{
     fn conditional_enforce_equal<CS: ConstraintSystem<ConstraintF>>(
         &self,
         mut cs: CS,
@@ -77,7 +79,9 @@ where
     fn cost() -> usize;
 }
 
-impl<ConstraintF: Field, T: Sized + ConditionalOrEqualsGadget<ConstraintF>> OrEqualsGadget<ConstraintF> for T {
+impl<ConstraintF: Field, T: Sized + ConditionalOrEqualsGadget<ConstraintF>>
+    OrEqualsGadget<ConstraintF> for T
+{
     fn enforce_equal_or<CS: ConstraintSystem<ConstraintF>>(
         cs: CS,
         cond: &Boolean,
@@ -109,8 +113,10 @@ where
     fn cost() -> usize;
 }
 
-impl<ConstraintF: Field, T: Sized + ConditionalEqGadget<ConstraintF> + CondSelectGadget<ConstraintF>>
-    ConditionalOrEqualsGadget<ConstraintF> for T
+impl<
+        ConstraintF: Field,
+        T: Sized + ConditionalEqGadget<ConstraintF> + CondSelectGadget<ConstraintF>,
+    > ConditionalOrEqualsGadget<ConstraintF> for T
 {
     fn conditional_enforce_equal_or<CS: ConstraintSystem<ConstraintF>>(
         mut cs: CS,
@@ -130,8 +136,7 @@ impl + CondSelec
     }
 
     fn cost() -> usize {
-        <Self as ConditionalEqGadget<ConstraintF>>::cost() + <Self as CondSelectGadget<ConstraintF>>::cost()
+        <Self as ConditionalEqGadget<ConstraintF>>::cost()
+            + <Self as CondSelectGadget<ConstraintF>>::cost()
     }
 }
-
-

r1cs-std/src/fields/bls12_377.rs

@@ -1,6 +1,4 @@
-use algebra::{
-    fields::bls12_377::{Fq, Fq12Parameters, Fq2Parameters, Fq6Parameters},
-};
+use algebra::fields::bls12_377::{Fq, Fq12Parameters, Fq2Parameters, Fq6Parameters};
 
 use super::{fp::FpGadget, fp12::Fp12Gadget, fp2::Fp2Gadget, fp6_3over2::Fp6Gadget};
 

r1cs-std/src/fields/edwards_bls12.rs

@@ -1,4 +1,4 @@
-use algebra::fields::edwards_bls12::fq::Fq;
 use crate::fields::fp::FpGadget;
+use algebra::fields::edwards_bls12::fq::Fq;
 
 pub type FqGadget = FpGadget<Fq>;

r1cs-std/src/fields/edwards_sw6.rs

@@ -1,4 +1,4 @@
-use algebra::fields::edwards_sw6::fq::Fq;
 use crate::fields::fp::FpGadget;
+use algebra::fields::edwards_sw6::fq::Fq;
 
 pub type FqGadget = FpGadget<Fq>;

r1cs-std/src/fields/fp.rs

@@ -1,12 +1,13 @@
 use algebra::{bytes::ToBytes, FpParameters, PrimeField};
-use r1cs_core::{ConstraintSystem, LinearCombination, SynthesisError, ConstraintVar::{self, *}};
+use r1cs_core::{
+    ConstraintSystem,
+    ConstraintVar::{self, *},
+    LinearCombination, SynthesisError,
+};
 
 use std::borrow::Borrow;
 
-use crate::boolean::AllocatedBit;
-use crate::Assignment;
-use crate::prelude::*;
-
+use crate::{boolean::AllocatedBit, prelude::*, Assignment};
 
 #[derive(Debug)]
 pub struct FpGadget<F: PrimeField> {
@@ -52,6 +53,23 @@ impl FieldGadget for FpGadget {
         })
     }
 
+    #[inline]
+    fn conditionally_add_constant<CS: ConstraintSystem<F>>(
+        &self,
+        mut _cs: CS,
+        bit: &Boolean,
+        coeff: F,
+    ) -> Result<Self, SynthesisError> {
+        let value = match (self.value, bit.get_value()) {
+            (Some(v), Some(b)) => Some(if b { v + &coeff } else { v }),
+            (..) => None,
+        };
+        Ok(FpGadget {
+            value,
+            variable: LC(bit.lc(CS::one(), coeff)) + &self.variable,
+        })
+    }
+
     #[inline]
     fn add<CS: ConstraintSystem<F>>(
         &self,
@@ -503,6 +521,52 @@ impl TwoBitLookupGadget for FpGadget {
     }
 }
 
+impl<F: PrimeField> ThreeBitCondNegLookupGadget<F> for FpGadget<F> {
+    type TableConstant = F;
+
+    fn three_bit_cond_neg_lookup<CS: ConstraintSystem<F>>(
+        mut cs: CS,
+        b: &[Boolean],
+        b0b1: &Boolean,
+        c: &[Self::TableConstant],
+    ) -> Result<Self, SynthesisError> {
+        debug_assert!(b.len() == 3);
+        debug_assert!(c.len() == 4);
+
+        let result = Self::alloc(cs.ns(|| "Allocate lookup result"), || {
+            let y = match (b[0].get_value().get()?, b[1].get_value().get()?) {
+                (false, false) => c[0],
+                (false, true) => c[2],
+                (true, false) => c[1],
+                (true, true) => c[3],
+            };
+            if b[2].get_value().get()? {
+                Ok(-y)
+            } else {
+                Ok(y)
+            }
+        })?;
+
+        let one = CS::one();
+        let y_lc = b0b1.lc(one, c[3] - &c[2] - &c[1] + &c[0])
+            + b[0].lc(one, c[1] - &c[0])
+            + b[1].lc(one, c[2] - &c[0])
+            + (c[0], one);
+        cs.enforce(
+            || "Enforce lookup",
+            |_| y_lc.clone() + y_lc.clone(),
+            |lc| lc + b[2].lc(one, F::one()),
+            |_| -result.get_variable() + y_lc.clone(),
+        );
+
+        Ok(result)
+    }
+
+    fn cost() -> usize {
+        2
+    }
+}
+
 impl<F: PrimeField> Clone for FpGadget<F> {
     fn clone(&self) -> Self {
         Self {

r1cs-std/src/fields/fp12.rs

@@ -1,24 +1,27 @@
 use r1cs_core::{ConstraintSystem, SynthesisError};
 
 use algebra::{
-    PrimeField, Field,
     fields::{
         fp12_2over3over2::{Fp12, Fp12Parameters},
         fp6_3over2::{Fp6, Fp6Parameters},
         Fp2Parameters,
     },
-    BitIterator,
+    BitIterator, Field, PrimeField,
 };
 use std::{borrow::Borrow, marker::PhantomData};
 
-use crate::prelude::*;
-use crate::Assignment;
+use crate::{prelude::*, Assignment};
 
-type Fp2Gadget<P, ConstraintF> =
-    super::fp2::Fp2Gadget<<<P as Fp12Parameters>::Fp6Params as Fp6Parameters>::Fp2Params, ConstraintF>;
-type Fp6Gadget<P, ConstraintF> = super::fp6_3over2::Fp6Gadget<<P as Fp12Parameters>::Fp6Params, ConstraintF>;
-type Fp6GadgetVariable<P, ConstraintF> =
-    <Fp6Gadget<P, ConstraintF> as FieldGadget<Fp6<<P as Fp12Parameters>::Fp6Params>, ConstraintF>>::Variable;
+type Fp2Gadget<P, ConstraintF> = super::fp2::Fp2Gadget<
+    <<P as Fp12Parameters>::Fp6Params as Fp6Parameters>::Fp2Params,
+    ConstraintF,
+>;
+type Fp6Gadget<P, ConstraintF> =
+    super::fp6_3over2::Fp6Gadget<<P as Fp12Parameters>::Fp6Params, ConstraintF>;
+type Fp6GadgetVariable<P, ConstraintF> = <Fp6Gadget<P, ConstraintF> as FieldGadget<
+    Fp6<<P as Fp12Parameters>::Fp6Params>,
+    ConstraintF,
+>>::Variable;
 
 #[derive(Derivative)]
 #[derivative(Debug(bound = "ConstraintF: PrimeField"))]
@@ -272,7 +275,10 @@ where
     P: Fp12Parameters,
     <P::Fp6Params as Fp6Parameters>::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
 {
-    type Variable = (Fp6GadgetVariable<P, ConstraintF>, Fp6GadgetVariable<P, ConstraintF>);
+    type Variable = (
+        Fp6GadgetVariable<P, ConstraintF>,
+        Fp6GadgetVariable<P, ConstraintF>,
+    );
 
     #[inline]
     fn get_value(&self) -> Option<Fp12<P>> {
@@ -298,6 +304,22 @@ where
         Ok(Self::new(c0, c1))
     }
 
+    #[inline]
+    fn conditionally_add_constant<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+        bit: &Boolean,
+        coeff: Fp12<P>,
+    ) -> Result<Self, SynthesisError> {
+        let c0 = self
+            .c0
+            .conditionally_add_constant(cs.ns(|| "c0"), bit, coeff.c0)?;
+        let c1 = self
+            .c1
+            .conditionally_add_constant(cs.ns(|| "c1"), bit, coeff.c1)?;
+        Ok(Self::new(c0, c1))
+    }
+
     #[inline]
     fn add<CS: ConstraintSystem<ConstraintF>>(
         &self,
@@ -343,7 +365,10 @@ where
     }
 
     #[inline]
-    fn negate<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn negate<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         let c0 = self.c0.negate(cs.ns(|| "c0"))?;
         let c1 = self.c1.negate(cs.ns(|| "c1"))?;
         Ok(Self::new(c0, c1))
@@ -396,7 +421,10 @@ where
         Ok(Self::new(c0, c1))
     }
 
-    fn square<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn square<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         // From Libsnark/fp2_gadget.tcc
         // Complex multiplication for Fp2:
         //     v0 = A.c0 * A.c1
@@ -518,7 +546,10 @@ where
         Ok(self)
     }
 
-    fn inverse<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn inverse<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         let inverse = Self::alloc(&mut cs.ns(|| "alloc inverse"), || {
             self.get_value().and_then(|val| val.inverse()).get()
         })?;
@@ -690,7 +721,10 @@ where
     P: Fp12Parameters,
     <P::Fp6Params as Fp6Parameters>::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
 {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         let mut c0 = self.c0.to_bits(&mut cs)?;
         let mut c1 = self.c1.to_bits(cs)?;
         c0.append(&mut c1);
@@ -713,7 +747,10 @@ where
     P: Fp12Parameters,
     <P::Fp6Params as Fp6Parameters>::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
 {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut c0 = self.c0.to_bytes(cs.ns(|| "c0"))?;
         let mut c1 = self.c1.to_bytes(cs.ns(|| "c1"))?;
         c0.append(&mut c1);
@@ -797,6 +834,42 @@ where
     }
 }
 
+impl<P, ConstraintF: PrimeField> ThreeBitCondNegLookupGadget<ConstraintF>
+    for Fp12Gadget<P, ConstraintF>
+where
+    P: Fp12Parameters,
+    <P::Fp6Params as Fp6Parameters>::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
+{
+    type TableConstant = Fp12<P>;
+
+    fn three_bit_cond_neg_lookup<CS: ConstraintSystem<ConstraintF>>(
+        mut cs: CS,
+        b: &[Boolean],
+        b0b1: &Boolean,
+        c: &[Self::TableConstant],
+    ) -> Result<Self, SynthesisError> {
+        let c0s = c.iter().map(|f| f.c0).collect::<Vec<_>>();
+        let c1s = c.iter().map(|f| f.c1).collect::<Vec<_>>();
+        let c0 = Fp6Gadget::<P, ConstraintF>::three_bit_cond_neg_lookup(
+            cs.ns(|| "Lookup c0"),
+            b,
+            b0b1,
+            &c0s,
+        )?;
+        let c1 = Fp6Gadget::<P, ConstraintF>::three_bit_cond_neg_lookup(
+            cs.ns(|| "Lookup c1"),
+            b,
+            b0b1,
+            &c1s,
+        )?;
+        Ok(Self::new(c0, c1))
+    }
+
+    fn cost() -> usize {
+        2 * <Fp6Gadget<P, ConstraintF> as ThreeBitCondNegLookupGadget<ConstraintF>>::cost()
+    }
+}
+
 impl<P, ConstraintF: PrimeField> AllocGadget<Fp12<P>, ConstraintF> for Fp12Gadget<P, ConstraintF>
 where
     P: Fp12Parameters,

r1cs-std/src/fields/fp2.rs

@@ -2,12 +2,10 @@ use algebra::{
     fields::{Fp2, Fp2Parameters},
     Field, PrimeField,
 };
-use r1cs_core::{ConstraintSystem, SynthesisError, ConstraintVar};
+use r1cs_core::{ConstraintSystem, ConstraintVar, SynthesisError};
 use std::{borrow::Borrow, marker::PhantomData};
 
-use crate::fields::fp::FpGadget;
-use crate::prelude::*;
-use crate::Assignment;
+use crate::{fields::fp::FpGadget, prelude::*, Assignment};
 
 #[derive(Derivative)]
 #[derivative(Debug(bound = "P: Fp2Parameters, ConstraintF: PrimeField"))]
@@ -62,7 +60,9 @@ impl, ConstraintF: PrimeField> Fp2Gadget
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> FieldGadget<Fp2<P>, ConstraintF> for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> FieldGadget<Fp2<P>, ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
     type Variable = (ConstraintVar<ConstraintF>, ConstraintVar<ConstraintF>);
 
     #[inline]
@@ -95,6 +95,22 @@ impl, ConstraintF: PrimeField> FieldGadget
         Ok(Self::new(c0, c1))
     }
 
+    #[inline]
+    fn conditionally_add_constant<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+        bit: &Boolean,
+        coeff: Fp2<P>,
+    ) -> Result<Self, SynthesisError> {
+        let c0 = self
+            .c0
+            .conditionally_add_constant(cs.ns(|| "c0"), bit, coeff.c0)?;
+        let c1 = self
+            .c1
+            .conditionally_add_constant(cs.ns(|| "c1"), bit, coeff.c1)?;
+        Ok(Self::new(c0, c1))
+    }
+
     #[inline]
     fn add<CS: ConstraintSystem<ConstraintF>>(
         &self,
@@ -191,7 +207,10 @@ impl, ConstraintF: PrimeField> FieldGadget
     }
 
     #[inline]
-    fn square<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn square<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         // From Libsnark/fp2_gadget.tcc
         // Complex multiplication for Fp2:
         //     v0 = A.c0 * A.c1
@@ -274,7 +293,10 @@ impl, ConstraintF: PrimeField> FieldGadget
     }
 
     #[inline]
-    fn inverse<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn inverse<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         let inverse = Self::alloc(&mut cs.ns(|| "alloc inverse"), || {
             self.get_value().and_then(|val| val.inverse()).get()
         })?;
@@ -439,7 +461,9 @@ impl, ConstraintF: PrimeField> FieldGadget
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> PartialEq for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> PartialEq
+    for Fp2Gadget<P, ConstraintF>
+{
     fn eq(&self, other: &Self) -> bool {
         self.c0 == other.c0 && self.c1 == other.c1
     }
@@ -447,9 +471,14 @@ impl, ConstraintF: PrimeField> PartialEq for
 
 impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> Eq for Fp2Gadget<P, ConstraintF> {}
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> EqGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {}
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> EqGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
+}
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> ConditionalEqGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> ConditionalEqGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
     #[inline]
     fn conditional_enforce_equal<CS: ConstraintSystem<ConstraintF>>(
         &self,
@@ -469,7 +498,9 @@ impl, ConstraintF: PrimeField> ConditionalEqG
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> NEqGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> NEqGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
     #[inline]
     fn enforce_not_equal<CS: ConstraintSystem<ConstraintF>>(
         &self,
@@ -486,8 +517,13 @@ impl, ConstraintF: PrimeField> NEqGadget
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> ToBitsGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> ToBitsGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         let mut c0 = self.c0.to_bits(&mut cs)?;
         let mut c1 = self.c1.to_bits(cs)?;
         c0.append(&mut c1);
@@ -505,8 +541,13 @@ impl, ConstraintF: PrimeField> ToBitsGadget
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> ToBytesGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> ToBytesGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut c0 = self.c0.to_bytes(cs.ns(|| "c0"))?;
         let mut c1 = self.c1.to_bytes(cs.ns(|| "c1"))?;
         c0.append(&mut c1);
@@ -524,7 +565,9 @@ impl, ConstraintF: PrimeField> ToBytesGadget<
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> Clone for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> Clone
+    for Fp2Gadget<P, ConstraintF>
+{
     fn clone(&self) -> Self {
         Self {
             c0:      self.c0.clone(),
@@ -534,7 +577,9 @@ impl, ConstraintF: PrimeField> Clone for Fp2G
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> CondSelectGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> CondSelectGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
     #[inline]
     fn conditionally_select<CS: ConstraintSystem<ConstraintF>>(
         mut cs: CS,
@@ -542,10 +587,18 @@ impl, ConstraintF: PrimeField> CondSelectGadg
         first: &Self,
         second: &Self,
     ) -> Result<Self, SynthesisError> {
-        let c0 =
-            FpGadget::<ConstraintF>::conditionally_select(&mut cs.ns(|| "c0"), cond, &first.c0, &second.c0)?;
-        let c1 =
-            FpGadget::<ConstraintF>::conditionally_select(&mut cs.ns(|| "c1"), cond, &first.c1, &second.c1)?;
+        let c0 = FpGadget::<ConstraintF>::conditionally_select(
+            &mut cs.ns(|| "c0"),
+            cond,
+            &first.c0,
+            &second.c0,
+        )?;
+        let c1 = FpGadget::<ConstraintF>::conditionally_select(
+            &mut cs.ns(|| "c1"),
+            cond,
+            &first.c1,
+            &second.c1,
+        )?;
 
         Ok(Self::new(c0, c1))
     }
@@ -555,7 +608,9 @@ impl, ConstraintF: PrimeField> CondSelectGadg
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> TwoBitLookupGadget<ConstraintF> for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> TwoBitLookupGadget<ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
     type TableConstant = Fp2<P>;
     fn two_bit_lookup<CS: ConstraintSystem<ConstraintF>>(
         mut cs: CS,
@@ -574,7 +629,32 @@ impl, ConstraintF: PrimeField> TwoBitLookupGa
     }
 }
 
-impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> AllocGadget<Fp2<P>, ConstraintF> for Fp2Gadget<P, ConstraintF> {
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField>
+    ThreeBitCondNegLookupGadget<ConstraintF> for Fp2Gadget<P, ConstraintF>
+{
+    type TableConstant = Fp2<P>;
+
+    fn three_bit_cond_neg_lookup<CS: ConstraintSystem<ConstraintF>>(
+        mut cs: CS,
+        b: &[Boolean],
+        b0b1: &Boolean,
+        c: &[Self::TableConstant],
+    ) -> Result<Self, SynthesisError> {
+        let c0s = c.iter().map(|f| f.c0).collect::<Vec<_>>();
+        let c1s = c.iter().map(|f| f.c1).collect::<Vec<_>>();
+        let c0 = FpGadget::three_bit_cond_neg_lookup(cs.ns(|| "Lookup c0"), b, b0b1, &c0s)?;
+        let c1 = FpGadget::three_bit_cond_neg_lookup(cs.ns(|| "Lookup c1"), b, b0b1, &c1s)?;
+        Ok(Self::new(c0, c1))
+    }
+
+    fn cost() -> usize {
+        2 * <FpGadget<ConstraintF> as ThreeBitCondNegLookupGadget<ConstraintF>>::cost()
+    }
+}
+
+impl<P: Fp2Parameters<Fp = ConstraintF>, ConstraintF: PrimeField> AllocGadget<Fp2<P>, ConstraintF>
+    for Fp2Gadget<P, ConstraintF>
+{
     #[inline]
     fn alloc<F, T, CS: ConstraintSystem<ConstraintF>>(
         mut cs: CS,

r1cs-std/src/fields/fp6_3over2.rs

@@ -5,13 +5,13 @@ use algebra::{
     },
     PrimeField,
 };
-use r1cs_core::{ConstraintSystem, SynthesisError, ConstraintVar};
+use r1cs_core::{ConstraintSystem, ConstraintVar, SynthesisError};
 use std::{borrow::Borrow, marker::PhantomData};
 
-use crate::prelude::*;
-use crate::Assignment;
+use crate::{prelude::*, Assignment};
 
-type Fp2Gadget<P, ConstraintF> = super::fp2::Fp2Gadget<<P as Fp6Parameters>::Fp2Params, ConstraintF>;
+type Fp2Gadget<P, ConstraintF> =
+    super::fp2::Fp2Gadget<<P as Fp6Parameters>::Fp2Params, ConstraintF>;
 
 #[derive(Derivative)]
 #[derivative(Debug(bound = "ConstraintF: PrimeField"))]
@@ -34,7 +34,11 @@ where
     P::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
 {
     #[inline]
-    pub fn new(c0: Fp2Gadget<P, ConstraintF>, c1: Fp2Gadget<P, ConstraintF>, c2: Fp2Gadget<P, ConstraintF>) -> Self {
+    pub fn new(
+        c0: Fp2Gadget<P, ConstraintF>,
+        c1: Fp2Gadget<P, ConstraintF>,
+        c2: Fp2Gadget<P, ConstraintF>,
+    ) -> Self {
         Self {
             c0,
             c1,
@@ -183,6 +187,25 @@ where
         Ok(Self::new(c0, c1, c2))
     }
 
+    #[inline]
+    fn conditionally_add_constant<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+        bit: &Boolean,
+        coeff: Fp6<P>,
+    ) -> Result<Self, SynthesisError> {
+        let c0 = self
+            .c0
+            .conditionally_add_constant(cs.ns(|| "c0"), bit, coeff.c0)?;
+        let c1 = self
+            .c1
+            .conditionally_add_constant(cs.ns(|| "c1"), bit, coeff.c1)?;
+        let c2 = self
+            .c2
+            .conditionally_add_constant(cs.ns(|| "c2"), bit, coeff.c2)?;
+        Ok(Self::new(c0, c1, c2))
+    }
+
     #[inline]
     fn add<CS: ConstraintSystem<ConstraintF>>(
         &self,
@@ -208,7 +231,10 @@ where
     }
 
     #[inline]
-    fn negate<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn negate<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         let c0 = self.c0.negate(&mut cs.ns(|| "negate c0"))?;
         let c1 = self.c1.negate(&mut cs.ns(|| "negate c1"))?;
         let c2 = self.c2.negate(&mut cs.ns(|| "negate c2"))?;
@@ -374,7 +400,10 @@ where
 
     /// Use the Toom-Cook-3x method to compute multiplication.
     #[inline]
-    fn square<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn square<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         // Uses Toom-Cool-3x multiplication from
         //
         // Reference:
@@ -473,7 +502,10 @@ where
 
     // 18 constaints, we can probably do better but not sure it's worth it.
     #[inline]
-    fn inverse<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn inverse<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         let inverse = Self::alloc(&mut cs.ns(|| "alloc inverse"), || {
             self.get_value().and_then(|val| val.inverse()).get()
         })?;
@@ -754,7 +786,10 @@ where
     P: Fp6Parameters,
     P::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
 {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         let mut c0 = self.c0.to_bits(&mut cs)?;
         let mut c1 = self.c1.to_bits(&mut cs)?;
         let mut c2 = self.c2.to_bits(cs)?;
@@ -785,7 +820,10 @@ where
     P: Fp6Parameters,
     P::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
 {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut c0 = self.c0.to_bytes(cs.ns(|| "c0"))?;
         let mut c1 = self.c1.to_bytes(cs.ns(|| "c1"))?;
         let mut c2 = self.c2.to_bytes(cs.ns(|| "c2"))?;
@@ -878,6 +916,49 @@ where
     }
 }
 
+impl<P, ConstraintF: PrimeField> ThreeBitCondNegLookupGadget<ConstraintF>
+    for Fp6Gadget<P, ConstraintF>
+where
+    P: Fp6Parameters,
+    P::Fp2Params: Fp2Parameters<Fp = ConstraintF>,
+{
+    type TableConstant = Fp6<P>;
+
+    fn three_bit_cond_neg_lookup<CS: ConstraintSystem<ConstraintF>>(
+        mut cs: CS,
+        b: &[Boolean],
+        b0b1: &Boolean,
+        c: &[Self::TableConstant],
+    ) -> Result<Self, SynthesisError> {
+        let c0s = c.iter().map(|f| f.c0).collect::<Vec<_>>();
+        let c1s = c.iter().map(|f| f.c1).collect::<Vec<_>>();
+        let c2s = c.iter().map(|f| f.c2).collect::<Vec<_>>();
+        let c0 = Fp2Gadget::<P, ConstraintF>::three_bit_cond_neg_lookup(
+            cs.ns(|| "Lookup c0"),
+            b,
+            b0b1,
+            &c0s,
+        )?;
+        let c1 = Fp2Gadget::<P, ConstraintF>::three_bit_cond_neg_lookup(
+            cs.ns(|| "Lookup c1"),
+            b,
+            b0b1,
+            &c1s,
+        )?;
+        let c2 = Fp2Gadget::<P, ConstraintF>::three_bit_cond_neg_lookup(
+            cs.ns(|| "Lookup c2"),
+            b,
+            b0b1,
+            &c2s,
+        )?;
+        Ok(Self::new(c0, c1, c2))
+    }
+
+    fn cost() -> usize {
+        3 * <Fp2Gadget<P, ConstraintF> as ThreeBitCondNegLookupGadget<ConstraintF>>::cost()
+    }
+}
+
 impl<P, ConstraintF: PrimeField> AllocGadget<Fp6<P>, ConstraintF> for Fp6Gadget<P, ConstraintF>
 where
     P: Fp6Parameters,

r1cs-std/src/fields/mod.rs

@@ -26,6 +26,7 @@ pub trait FieldGadget:
     + ToBytesGadget<ConstraintF>
     + CondSelectGadget<ConstraintF>
     + TwoBitLookupGadget<ConstraintF, TableConstant = F>
+    + ThreeBitCondNegLookupGadget<ConstraintF, TableConstant = F>
     + Debug
 {
     type Variable: Clone + Debug;
@@ -38,7 +39,18 @@ pub trait FieldGadget:
 
     fn one<CS: ConstraintSystem<ConstraintF>>(_: CS) -> Result<Self, SynthesisError>;
 
-    fn add<CS: ConstraintSystem<ConstraintF>>(&self, _: CS, _: &Self) -> Result<Self, SynthesisError>;
+    fn conditionally_add_constant<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _: CS,
+        _: &Boolean,
+        _: F,
+    ) -> Result<Self, SynthesisError>;
+
+    fn add<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _: CS,
+        _: &Self,
+    ) -> Result<Self, SynthesisError>;
 
     fn add_in_place<CS: ConstraintSystem<ConstraintF>>(
         &mut self,
@@ -61,7 +73,11 @@ pub trait FieldGadget:
         Ok(self)
     }
 
-    fn sub<CS: ConstraintSystem<ConstraintF>>(&self, _: CS, _: &Self) -> Result<Self, SynthesisError>;
+    fn sub<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _: CS,
+        _: &Self,
+    ) -> Result<Self, SynthesisError>;
 
     fn sub_in_place<CS: ConstraintSystem<ConstraintF>>(
         &mut self,
@@ -83,7 +99,11 @@ pub trait FieldGadget:
         Ok(self)
     }
 
-    fn mul<CS: ConstraintSystem<ConstraintF>>(&self, _: CS, _: &Self) -> Result<Self, SynthesisError>;
+    fn mul<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _: CS,
+        _: &Self,
+    ) -> Result<Self, SynthesisError>;
 
     fn mul_in_place<CS: ConstraintSystem<ConstraintF>>(
         &mut self,
@@ -125,7 +145,11 @@ pub trait FieldGadget:
         result.enforce_equal(&mut cs.ns(|| "test_equals"), &actual_result)
     }
 
-    fn add_constant<CS: ConstraintSystem<ConstraintF>>(&self, _: CS, _: &F) -> Result<Self, SynthesisError>;
+    fn add_constant<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        _: CS,
+        _: &F,
+    ) -> Result<Self, SynthesisError>;
 
     fn add_constant_in_place<CS: ConstraintSystem<ConstraintF>>(
         &mut self,
@@ -217,10 +241,15 @@ mod test {
     use rand_xorshift::XorShiftRng;
 
     use crate::{prelude::*, test_constraint_system::TestConstraintSystem};
-    use algebra::{UniformRand, Field, BitIterator};
+    use algebra::{BitIterator, Field, UniformRand};
     use r1cs_core::ConstraintSystem;
 
-    fn field_test<FE: Field, ConstraintF: Field, F: FieldGadget<FE, ConstraintF>, CS: ConstraintSystem<ConstraintF>>(
+    fn field_test<
+        FE: Field,
+        ConstraintF: Field,
+        F: FieldGadget<FE, ConstraintF>,
+        CS: ConstraintSystem<ConstraintF>,
+    >(
         mut cs: CS,
         a: F,
         b: F,
@@ -402,6 +431,23 @@ mod test {
         let n = F::alloc(&mut cs.ns(|| "alloc new var"), || Ok(negone)).unwrap();
         let _ = n.to_bytes(&mut cs.ns(|| "ToBytes")).unwrap();
         let _ = n.to_bytes_strict(&mut cs.ns(|| "ToBytes Strict")).unwrap();
+
+        let ab_false = a
+            .conditionally_add_constant(
+                cs.ns(|| "Add bool with coeff false"),
+                &Boolean::constant(false),
+                b_native,
+            )
+            .unwrap();
+        assert_eq!(ab_false.get_value().unwrap(), a_native);
+        let ab_true = a
+            .conditionally_add_constant(
+                cs.ns(|| "Add bool with coeff true"),
+                &Boolean::constant(true),
+                b_native,
+            )
+            .unwrap();
+        assert_eq!(ab_true.get_value().unwrap(), a_native + &b_native);
     }
 
     fn random_frobenius_tests<

r1cs-std/src/groups/curves/short_weierstrass/bls12/bls12_377.rs

@@ -15,11 +15,10 @@ mod test {
     use rand;
 
     use super::{G1Gadget, G2Gadget};
-    use crate::{test_constraint_system::TestConstraintSystem, prelude::*};
+    use crate::{prelude::*, test_constraint_system::TestConstraintSystem};
     use algebra::{
         curves::bls12_377::{G1Projective as G1, G2Projective as G2},
-        fields::bls12_377::Fr,
-        fields::bls12_377::Fq,
+        fields::bls12_377::{Fq, Fr},
         AffineCurve, BitIterator, PrimeField, ProjectiveCurve,
     };
     use r1cs_core::ConstraintSystem;
@@ -52,10 +51,7 @@ mod test {
         let add_cost = cs.num_constraints() - cond_select_cost - alloc_cost;
 
         assert!(cs.is_satisfied());
-        assert_eq!(
-            cond_select_cost,
-            <G1Gadget as CondSelectGadget<Fq>>::cost()
-        );
+        assert_eq!(cond_select_cost, <G1Gadget as CondSelectGadget<Fq>>::cost());
         assert_eq!(add_cost, G1Gadget::cost_of_add());
     }
 
@@ -87,10 +83,7 @@ mod test {
         let add_cost = cs.num_constraints() - cond_select_cost - alloc_cost;
 
         assert!(cs.is_satisfied());
-        assert_eq!(
-            cond_select_cost,
-            <G2Gadget as CondSelectGadget<Fq>>::cost()
-        );
+        assert_eq!(cond_select_cost, <G2Gadget as CondSelectGadget<Fq>>::cost());
         assert_eq!(add_cost, G2Gadget::cost_of_add());
     }
 

r1cs-std/src/groups/curves/short_weierstrass/bls12/mod.rs

@@ -5,17 +5,23 @@ use algebra::{
 };
 use r1cs_core::{ConstraintSystem, SynthesisError};
 
-
-use crate::prelude::*;
-use crate::fields::{fp::FpGadget, fp2::Fp2Gadget, FieldGadget};
-use crate::groups::curves::short_weierstrass::AffineGadget;
+use crate::{
+    fields::{fp::FpGadget, fp2::Fp2Gadget, FieldGadget},
+    groups::curves::short_weierstrass::AffineGadget,
+    prelude::*,
+};
 
 use std::fmt::Debug;
 
 pub mod bls12_377;
 
-pub type G1Gadget<P> = AffineGadget<<P as Bls12Parameters>::G1Parameters, <P as Bls12Parameters>::Fp, FpGadget<<P as Bls12Parameters>::Fp>>;
-pub type G2Gadget<P> = AffineGadget<<P as Bls12Parameters>::G2Parameters, <P as Bls12Parameters>::Fp, Fp2G<P>>;
+pub type G1Gadget<P> = AffineGadget<
+    <P as Bls12Parameters>::G1Parameters,
+    <P as Bls12Parameters>::Fp,
+    FpGadget<<P as Bls12Parameters>::Fp>,
+>;
+pub type G2Gadget<P> =
+    AffineGadget<<P as Bls12Parameters>::G2Parameters, <P as Bls12Parameters>::Fp, Fp2G<P>>;
 
 #[derive(Derivative)]
 #[derivative(
@@ -41,7 +47,10 @@ impl G1PreparedGadget
 
 impl<P: Bls12Parameters> ToBytesGadget<P::Fp> for G1PreparedGadget<P> {
     #[inline]
-    fn to_bytes<CS: ConstraintSystem<P::Fp>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<P::Fp>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         self.0.to_bytes(&mut cs.ns(|| "g_alpha to bytes"))
     }
 
@@ -66,7 +75,10 @@ pub struct G2PreparedGadget {
 
 impl<P: Bls12Parameters> ToBytesGadget<P::Fp> for G2PreparedGadget<P> {
     #[inline]
-    fn to_bytes<CS: ConstraintSystem<P::Fp>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<P::Fp>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut bytes = Vec::new();
         for (i, coeffs) in self.ell_coeffs.iter().enumerate() {
             let mut cs = cs.ns(|| format!("Iteration {}", i));

r1cs-std/src/groups/curves/short_weierstrass/mod.rs

@@ -1,23 +1,25 @@
-use algebra::{AffineCurve, Field, ProjectiveCurve};
 use algebra::{
     curves::{
         short_weierstrass_jacobian::{GroupAffine as SWAffine, GroupProjective as SWProjective},
         SWModelParameters,
     },
-    BitIterator, PrimeField,
+    AffineCurve, BitIterator, Field, PrimeField, ProjectiveCurve,
 };
 use r1cs_core::{ConstraintSystem, SynthesisError};
 use std::{borrow::Borrow, marker::PhantomData, ops::Neg};
 
-use crate::Assignment;
-use crate::prelude::*;
+use crate::{prelude::*, Assignment};
 
 pub mod bls12;
 
 #[derive(Derivative)]
 #[derivative(Debug, Clone)]
 #[must_use]
-pub struct AffineGadget<P: SWModelParameters, ConstraintF: Field, F: FieldGadget<P::BaseField, ConstraintF>> {
+pub struct AffineGadget<
+    P: SWModelParameters,
+    ConstraintF: Field,
+    F: FieldGadget<P::BaseField, ConstraintF>,
+> {
     pub x:   F,
     pub y:   F,
     _params: PhantomData<P>,
@@ -80,7 +82,8 @@ where
 {
 }
 
-impl<P, ConstraintF, F> GroupGadget<SWProjective<P>, ConstraintF> for AffineGadget<P, ConstraintF, F>
+impl<P, ConstraintF, F> GroupGadget<SWProjective<P>, ConstraintF>
+    for AffineGadget<P, ConstraintF, F>
 where
     P: SWModelParameters,
     ConstraintF: Field,
@@ -297,7 +300,10 @@ where
         Ok(())
     }
 
-    fn negate<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+    fn negate<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Self, SynthesisError> {
         Ok(Self::new(
             self.x.clone(),
             self.y.negate(cs.ns(|| "negate y"))?,
@@ -400,7 +406,8 @@ where
     }
 }
 
-impl<P, ConstraintF, F> AllocGadget<SWProjective<P>, ConstraintF> for AffineGadget<P, ConstraintF, F>
+impl<P, ConstraintF, F> AllocGadget<SWProjective<P>, ConstraintF>
+    for AffineGadget<P, ConstraintF, F>
 where
     P: SWModelParameters,
     ConstraintF: Field,
@@ -572,7 +579,10 @@ where
     ConstraintF: Field,
     F: FieldGadget<P::BaseField, ConstraintF>,
 {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         let mut x_bits = self.x.to_bits(&mut cs.ns(|| "X Coordinate To Bits"))?;
         let y_bits = self.y.to_bits(&mut cs.ns(|| "Y Coordinate To Bits"))?;
         x_bits.extend_from_slice(&y_bits);
@@ -601,7 +611,10 @@ where
     ConstraintF: Field,
     F: FieldGadget<P::BaseField, ConstraintF>,
 {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut x_bytes = self.x.to_bytes(&mut cs.ns(|| "X Coordinate To Bytes"))?;
         let y_bytes = self.y.to_bytes(&mut cs.ns(|| "Y Coordinate To Bytes"))?;
         x_bytes.extend_from_slice(&y_bytes);

r1cs-std/src/groups/curves/twisted_edwards/edwards_bls12.rs

@@ -1,6 +1,5 @@
 use crate::groups::curves::twisted_edwards::AffineGadget;
-use algebra::curves::edwards_bls12::EdwardsParameters;
-use algebra::fields::edwards_bls12::fq::Fq;
+use algebra::{curves::edwards_bls12::EdwardsParameters, fields::edwards_bls12::fq::Fq};
 
 use crate::fields::edwards_bls12::FqGadget;
 
@@ -13,8 +12,7 @@ mod test {
         groups::curves::twisted_edwards::test::{edwards_constraint_costs, edwards_test},
         test_constraint_system::TestConstraintSystem,
     };
-    use algebra::fields::edwards_bls12::fq::Fq;
-    use algebra::curves::edwards_bls12::EdwardsParameters;
+    use algebra::{curves::edwards_bls12::EdwardsParameters, fields::edwards_bls12::fq::Fq};
 
     #[test]
     fn edwards_constraint_costs_test() {

r1cs-std/src/groups/curves/twisted_edwards/edwards_sw6.rs

@@ -1,6 +1,5 @@
 use crate::groups::curves::twisted_edwards::AffineGadget;
-use algebra::curves::edwards_sw6::EdwardsParameters;
-use algebra::fields::edwards_sw6::fq::Fq;
+use algebra::{curves::edwards_sw6::EdwardsParameters, fields::edwards_sw6::fq::Fq};
 
 use crate::fields::edwards_sw6::FqGadget;
 
@@ -13,8 +12,7 @@ mod test {
         groups::curves::twisted_edwards::test::{edwards_constraint_costs, edwards_test},
         test_constraint_system::TestConstraintSystem,
     };
-    use algebra::curves::edwards_sw6::EdwardsParameters;
-    use algebra::fields::edwards_sw6::fq::Fq;
+    use algebra::{curves::edwards_sw6::EdwardsParameters, fields::edwards_sw6::fq::Fq};
 
     #[test]
     fn edwards_constraint_costs_test() {

r1cs-std/src/groups/curves/twisted_edwards/jubjub.rs

@@ -1,6 +1,5 @@
 use crate::groups::curves::twisted_edwards::AffineGadget;
-use algebra::curves::jubjub::JubJubParameters;
-use algebra::fields::jubjub::fq::Fq;
+use algebra::{curves::jubjub::JubJubParameters, fields::jubjub::fq::Fq};
 
 use crate::fields::jubjub::FqGadget;
 
@@ -13,8 +12,7 @@ mod test {
         groups::curves::twisted_edwards::test::{edwards_constraint_costs, edwards_test},
         test_constraint_system::TestConstraintSystem,
     };
-    use algebra::fields::jubjub::fq::Fq;
-    use algebra::curves::jubjub::JubJubParameters as EdwardsParameters;
+    use algebra::{curves::jubjub::JubJubParameters as EdwardsParameters, fields::jubjub::fq::Fq};
 
     #[test]
     fn edwards_constraint_costs_test() {

r1cs-std/src/groups/curves/twisted_edwards/mod.rs

@@ -1,6 +1,9 @@
 use algebra::{
-    curves::{twisted_edwards_extended::GroupAffine as TEAffine, TEModelParameters},
-    BitIterator, Field
+    curves::{
+        twisted_edwards_extended::GroupAffine as TEAffine, MontgomeryModelParameters,
+        TEModelParameters,
+    },
+    BitIterator, Field,
 };
 
 use r1cs_core::{ConstraintSystem, SynthesisError};
@@ -19,9 +22,187 @@ mod test;
 #[derivative(Debug, Clone)]
 #[derivative(Debug(bound = "P: TEModelParameters, ConstraintF: Field"))]
 #[must_use]
-pub struct AffineGadget<P: TEModelParameters, ConstraintF: Field, F: FieldGadget<P::BaseField, ConstraintF>> {
-    pub x:   F,
-    pub y:   F,
+pub struct MontgomeryAffineGadget<
+    P: TEModelParameters,
+    ConstraintF: Field,
+    F: FieldGadget<P::BaseField, ConstraintF>,
+> {
+    pub x: F,
+    pub y: F,
+    #[derivative(Debug = "ignore")]
+    _params: PhantomData<P>,
+    #[derivative(Debug = "ignore")]
+    _engine: PhantomData<ConstraintF>,
+}
+
+mod montgomery_affine_impl {
+    use super::*;
+    use crate::Assignment;
+    use algebra::{twisted_edwards_extended::GroupAffine, AffineCurve, Field};
+    use std::ops::{AddAssign, MulAssign, SubAssign};
+
+    impl<P: TEModelParameters, ConstraintF: Field, F: FieldGadget<P::BaseField, ConstraintF>>
+        MontgomeryAffineGadget<P, ConstraintF, F>
+    {
+        pub fn new(x: F, y: F) -> Self {
+            Self {
+                x,
+                y,
+                _params: PhantomData,
+                _engine: PhantomData,
+            }
+        }
+
+        pub fn from_edwards_to_coords(
+            p: &TEAffine<P>,
+        ) -> Result<(P::BaseField, P::BaseField), SynthesisError> {
+            let montgomery_point: GroupAffine<P> = if p.y == P::BaseField::one() {
+                GroupAffine::zero()
+            } else {
+                if p.x == P::BaseField::zero() {
+                    GroupAffine::new(P::BaseField::zero(), P::BaseField::zero())
+                } else {
+                    let u = (P::BaseField::one() + &p.y)
+                        * &(P::BaseField::one() - &p.y).inverse().unwrap();
+                    let v = u * &p.x.inverse().unwrap();
+                    GroupAffine::new(u, v)
+                }
+            };
+
+            Ok((montgomery_point.x, montgomery_point.y))
+        }
+
+        pub fn from_edwards<CS: ConstraintSystem<ConstraintF>>(
+            mut cs: CS,
+            p: &TEAffine<P>,
+        ) -> Result<Self, SynthesisError> {
+            let montgomery_coords = Self::from_edwards_to_coords(p)?;
+
+            let u = F::alloc(cs.ns(|| "u"), || Ok(montgomery_coords.0))?;
+
+            let v = F::alloc(cs.ns(|| "v"), || Ok(montgomery_coords.1))?;
+
+            Ok(Self::new(u, v))
+        }
+
+        pub fn into_edwards<CS: ConstraintSystem<ConstraintF>>(
+            &self,
+            mut cs: CS,
+        ) -> Result<AffineGadget<P, ConstraintF, F>, SynthesisError> {
+            // Compute u = x / y
+            let u = F::alloc(cs.ns(|| "u"), || {
+                let mut t0 = self.x.get_value().get()?;
+
+                match self.y.get_value().get()?.inverse() {
+                    Some(invy) => {
+                        t0.mul_assign(&invy);
+
+                        Ok(t0)
+                    },
+                    None => Err(SynthesisError::DivisionByZero),
+                }
+            })?;
+
+            u.mul_equals(cs.ns(|| "u equals"), &self.y, &self.x)?;
+
+            let v = F::alloc(cs.ns(|| "v"), || {
+                let mut t0 = self.x.get_value().get()?;
+                let mut t1 = t0.clone();
+                t0.sub_assign(&P::BaseField::one());
+                t1.add_assign(&P::BaseField::one());
+
+                match t1.inverse() {
+                    Some(t1) => {
+                        t0.mul_assign(&t1);
+
+                        Ok(t0)
+                    },
+                    None => Err(SynthesisError::DivisionByZero),
+                }
+            })?;
+
+            let xplusone = self
+                .x
+                .add_constant(cs.ns(|| "x plus one"), &P::BaseField::one())?;
+            let xminusone = self
+                .x
+                .sub_constant(cs.ns(|| "x minus one"), &P::BaseField::one())?;
+            v.mul_equals(cs.ns(|| "v equals"), &xplusone, &xminusone)?;
+
+            Ok(AffineGadget::new(u, v))
+        }
+
+        pub fn add<CS: ConstraintSystem<ConstraintF>>(
+            &self,
+            mut cs: CS,
+            other: &Self,
+        ) -> Result<Self, SynthesisError> {
+            let lambda = F::alloc(cs.ns(|| "lambda"), || {
+                let mut n = other.y.get_value().get()?;
+                n.sub_assign(&self.y.get_value().get()?);
+
+                let mut d = other.x.get_value().get()?;
+                d.sub_assign(&self.x.get_value().get()?);
+
+                match d.inverse() {
+                    Some(d) => {
+                        n.mul_assign(&d);
+                        Ok(n)
+                    },
+                    None => Err(SynthesisError::DivisionByZero),
+                }
+            })?;
+            let lambda_n = other.y.sub(cs.ns(|| "other.y - self.y"), &self.y)?;
+            let lambda_d = other.x.sub(cs.ns(|| "other.x - self.x"), &self.x)?;
+            lambda_d.mul_equals(cs.ns(|| "lambda equals"), &lambda, &lambda_n)?;
+
+            // Compute x'' = B*lambda^2 - A - x - x'
+            let xprime = F::alloc(cs.ns(|| "xprime"), || {
+                Ok(
+                    lambda.get_value().get()?.square() * &P::MontgomeryModelParameters::COEFF_B
+                        - &P::MontgomeryModelParameters::COEFF_A
+                        - &self.x.get_value().get()?
+                        - &other.x.get_value().get()?,
+                )
+            })?;
+
+            let xprime_lc = self
+                .x
+                .add(cs.ns(|| "self.x + other.x"), &other.x)?
+                .add(cs.ns(|| "+ xprime"), &xprime)?
+                .add_constant(cs.ns(|| "+ A"), &P::MontgomeryModelParameters::COEFF_A)?;
+            // (lambda) * (lambda) = (A + x + x' + x'')
+            let lambda_b = lambda.mul_by_constant(
+                cs.ns(|| "lambda * b"),
+                &P::MontgomeryModelParameters::COEFF_B,
+            )?;
+            lambda_b.mul_equals(cs.ns(|| "xprime equals"), &lambda, &xprime_lc)?;
+
+            let yprime = F::alloc(cs.ns(|| "yprime"), || {
+                Ok(-(self.y.get_value().get()?
+                    + &(lambda.get_value().get()?
+                        * &(xprime.get_value().get()? - &self.x.get_value().get()?))))
+            })?;
+
+            let xres = self.x.sub(cs.ns(|| "xres"), &xprime)?;
+            let yres = self.y.add(cs.ns(|| "yres"), &yprime)?;
+            lambda.mul_equals(cs.ns(|| "yprime equals"), &xres, &yres)?;
+            Ok(MontgomeryAffineGadget::new(xprime, yprime))
+        }
+    }
+}
+
+#[derive(Derivative)]
+#[derivative(Debug, Clone)]
+#[derivative(Debug(bound = "P: TEModelParameters, ConstraintF: Field"))]
+#[must_use]
+pub struct AffineGadget<
+    P: TEModelParameters,
+    ConstraintF: Field,
+    F: FieldGadget<P::BaseField, ConstraintF>,
+> {
+    pub x: F,
+    pub y: F,
     #[derivative(Debug = "ignore")]
     _params: PhantomData<P>,
     #[derivative(Debug = "ignore")]
@@ -293,7 +474,10 @@ mod affine_impl {
             Ok(())
         }
 
-        fn negate<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+        fn negate<CS: ConstraintSystem<ConstraintF>>(
+            &self,
+            mut cs: CS,
+        ) -> Result<Self, SynthesisError> {
             Ok(Self::new(
                 self.x.negate(cs.ns(|| "negate x"))?,
                 self.y.clone(),
@@ -487,7 +671,8 @@ mod projective_impl {
     };
     use std::ops::Neg;
 
-    impl<P, ConstraintF, F> GroupGadget<TEProjective<P>, ConstraintF> for AffineGadget<P, ConstraintF, F>
+    impl<P, ConstraintF, F> GroupGadget<TEProjective<P>, ConstraintF>
+        for AffineGadget<P, ConstraintF, F>
     where
         P: TEModelParameters,
         ConstraintF: Field,
@@ -694,7 +879,10 @@ mod projective_impl {
             Ok(())
         }
 
-        fn negate<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Self, SynthesisError> {
+        fn negate<CS: ConstraintSystem<ConstraintF>>(
+            &self,
+            mut cs: CS,
+        ) -> Result<Self, SynthesisError> {
             Ok(Self::new(
                 self.x.negate(cs.ns(|| "negate x"))?,
                 self.y.clone(),
@@ -757,6 +945,141 @@ mod projective_impl {
             Ok(())
         }
 
+        fn precomputed_base_3_bit_signed_digit_scalar_mul<'a, CS, I, J, B>(
+            mut cs: CS,
+            bases: &[B],
+            scalars: &[J],
+        ) -> Result<Self, SynthesisError>
+        where
+            CS: ConstraintSystem<ConstraintF>,
+            I: Borrow<[Boolean]>,
+            J: Borrow<[I]>,
+            B: Borrow<[TEProjective<P>]>,
+        {
+            const CHUNK_SIZE: usize = 3;
+            let mut edwards_result: Option<AffineGadget<P, ConstraintF, F>> = None;
+            let mut result: Option<MontgomeryAffineGadget<P, ConstraintF, F>> = None;
+
+            let mut process_segment_result =
+                |mut cs: r1cs_core::Namespace<_, _>,
+                 result: &MontgomeryAffineGadget<P, ConstraintF, F>|
+                 -> Result<(), SynthesisError> {
+                    let segment_result = result.into_edwards(cs.ns(|| "segment result"))?;
+                    match edwards_result {
+                        None => {
+                            edwards_result = Some(segment_result);
+                        },
+                        Some(ref mut edwards_result) => {
+                            *edwards_result = GroupGadget::<TEAffine<P>, ConstraintF>::add(
+                                &segment_result,
+                                cs.ns(|| "edwards addition"),
+                                edwards_result,
+                            )?;
+                        },
+                    }
+
+                    Ok(())
+                };
+
+            // Compute ∏(h_i^{m_i}) for all i.
+            for (segment_i, (segment_bits_chunks, segment_powers)) in
+                scalars.into_iter().zip(bases.iter()).enumerate()
+            {
+                for (i, (bits, base_power)) in segment_bits_chunks
+                    .borrow()
+                    .into_iter()
+                    .zip(segment_powers.borrow().iter())
+                    .enumerate()
+                {
+                    let base_power = base_power.borrow();
+                    let mut acc_power = *base_power;
+                    let mut coords = vec![];
+                    for _ in 0..4 {
+                        coords.push(acc_power);
+                        acc_power = acc_power + base_power;
+                    }
+
+                    let bits = bits.borrow().to_bits(
+                        &mut cs.ns(|| format!("Convert Scalar {}, {} to bits", segment_i, i)),
+                    )?;
+                    if bits.len() != CHUNK_SIZE {
+                        return Err(SynthesisError::Unsatisfiable);
+                    }
+
+                    let coords = coords
+                        .iter()
+                        .map(|p| {
+                            let p = p.into_affine();
+                            MontgomeryAffineGadget::<P, ConstraintF, F>::from_edwards_to_coords(&p)
+                                .unwrap()
+                        })
+                        .collect::<Vec<_>>();
+
+                    let x_coeffs = coords.iter().map(|p| p.0).collect::<Vec<_>>();
+                    let y_coeffs = coords.iter().map(|p| p.1).collect::<Vec<_>>();
+
+                    let precomp = Boolean::and(
+                        cs.ns(|| format!("precomp in window {}, {}", segment_i, i)),
+                        &bits[0],
+                        &bits[1],
+                    )?;
+
+                    let x = F::zero(cs.ns(|| format!("x in window {}, {}", segment_i, i)))?
+                        .conditionally_add_constant(
+                            cs.ns(|| format!("add bool 00 in window {}, {}", segment_i, i)),
+                            &Boolean::constant(true),
+                            x_coeffs[0],
+                        )?
+                        .conditionally_add_constant(
+                            cs.ns(|| format!("add bool 01 in window {}, {}", segment_i, i)),
+                            &bits[0],
+                            x_coeffs[1] - &x_coeffs[0],
+                        )?
+                        .conditionally_add_constant(
+                            cs.ns(|| format!("add bool 10 in window {}, {}", segment_i, i)),
+                            &bits[1],
+                            x_coeffs[2] - &x_coeffs[0],
+                        )?
+                        .conditionally_add_constant(
+                            cs.ns(|| format!("add bool 11 in window {}, {}", segment_i, i)),
+                            &precomp,
+                            x_coeffs[3] - &x_coeffs[2] - &x_coeffs[1] + &x_coeffs[0],
+                        )?;
+
+                    let y = F::three_bit_cond_neg_lookup(
+                        cs.ns(|| format!("y lookup in window {}, {}", segment_i, i)),
+                        &bits,
+                        &precomp,
+                        &y_coeffs,
+                    )?;
+
+                    let tmp = MontgomeryAffineGadget::new(x, y);
+
+                    match result {
+                        None => {
+                            result = Some(tmp);
+                        },
+                        Some(ref mut result) => {
+                            *result = tmp.add(
+                                cs.ns(|| format!("addition of window {}, {}", segment_i, i)),
+                                result,
+                            )?;
+                        },
+                    }
+                }
+
+                process_segment_result(
+                    cs.ns(|| format!("window {}", segment_i)),
+                    &result.unwrap(),
+                )?;
+                result = None;
+            }
+            if result.is_some() {
+                process_segment_result(cs.ns(|| "leftover"), &result.unwrap())?;
+            }
+            Ok(edwards_result.unwrap())
+        }
+
         fn cost_of_add() -> usize {
             4 + 2 * F::cost_of_mul()
         }
@@ -766,7 +1089,8 @@ mod projective_impl {
         }
     }
 
-    impl<P, ConstraintF, F> AllocGadget<TEProjective<P>, ConstraintF> for AffineGadget<P, ConstraintF, F>
+    impl<P, ConstraintF, F> AllocGadget<TEProjective<P>, ConstraintF>
+        for AffineGadget<P, ConstraintF, F>
     where
         P: TEModelParameters,
         ConstraintF: Field,
@@ -1033,7 +1357,10 @@ where
     ConstraintF: Field,
     F: FieldGadget<P::BaseField, ConstraintF>,
 {
-    fn to_bits<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<Boolean>, SynthesisError> {
+    fn to_bits<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<Boolean>, SynthesisError> {
         let mut x_bits = self.x.to_bits(cs.ns(|| "X Coordinate To Bits"))?;
         let y_bits = self.y.to_bits(cs.ns(|| "Y Coordinate To Bits"))?;
         x_bits.extend_from_slice(&y_bits);
@@ -1058,7 +1385,10 @@ where
     ConstraintF: Field,
     F: FieldGadget<P::BaseField, ConstraintF>,
 {
-    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(&self, mut cs: CS) -> Result<Vec<UInt8>, SynthesisError> {
+    fn to_bytes<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        mut cs: CS,
+    ) -> Result<Vec<UInt8>, SynthesisError> {
         let mut x_bytes = self.x.to_bytes(cs.ns(|| "x"))?;
         let y_bytes = self.y.to_bytes(cs.ns(|| "y"))?;
         x_bytes.extend_from_slice(&y_bytes);

r1cs-std/src/groups/curves/twisted_edwards/test.rs

@@ -1,10 +1,10 @@
 use rand::thread_rng;
 
-use crate::{prelude::*, groups::test::group_test};
+use crate::{groups::test::group_test, prelude::*};
 
 use algebra::{
     curves::{models::TEModelParameters, twisted_edwards_extended::GroupAffine as TEAffine},
-    BitIterator, Group, PrimeField, Field, UniformRand,
+    BitIterator, Field, Group, PrimeField, UniformRand,
 };
 
 use r1cs_core::ConstraintSystem;

r1cs-std/src/groups/mod.rs

@@ -1,5 +1,5 @@
 use crate::prelude::*;
-use algebra::{Group, Field};
+use algebra::{Field, Group};
 use r1cs_core::{ConstraintSystem, SynthesisError};
 
 use std::{borrow::Borrow, fmt::Debug};
@@ -31,7 +31,11 @@ pub trait GroupGadget:
 
     fn zero<CS: ConstraintSystem<ConstraintF>>(cs: CS) -> Result<Self, SynthesisError>;
 
-    fn add<CS: ConstraintSystem<ConstraintF>>(&self, cs: CS, other: &Self) -> Result<Self, SynthesisError>;
+    fn add<CS: ConstraintSystem<ConstraintF>>(
+        &self,
+        cs: CS,
+        other: &Self,
+    ) -> Result<Self, SynthesisError>;
 
     fn sub<CS: ConstraintSystem<ConstraintF>>(
         &self,
@@ -57,7 +61,10 @@ pub trait GroupGadget:
         self.add_constant(cs.ns(|| "Self - other"), &neg_other)
     }
 
-    fn double_in_place<CS: ConstraintSystem<ConstraintF>>(&mut self, cs: CS) -> Result<(), SynthesisError>;
+    fn double_in_place<CS: ConstraintSystem<ConstraintF>>(
+        &mut self,
+        cs: CS,
+    ) -> Result<(), SynthesisError>;
 
     fn negate<CS: ConstraintSystem<ConstraintF>>(&self, cs: CS) -> Result<Self, SynthesisError>;
 
@@ -111,6 +118,20 @@ pub trait GroupGadget:
         Ok(())
     }
 
+    fn precomputed_base_3_bit_signed_digit_scalar_mul<'a, CS, I, J, B>(
+        _: CS,
+        _: &[B],
+        _: &[J],
+    ) -> Result<Self, SynthesisError>
+    where
+        CS: ConstraintSystem<ConstraintF>,
+        I: Borrow<[Boolean]>,
+        J: Borrow<[I]>,
+        B: Borrow<[G]>,
+    {
+        Err(SynthesisError::AssignmentMissing)
+    }
+
     fn precomputed_base_multiscalar_mul<'a, CS, T, I, B>(
         mut cs: CS,
         bases: &[B],
@@ -145,9 +166,7 @@ mod test {
     use algebra::Field;
     use r1cs_core::ConstraintSystem;
 
-    use crate::{
-        prelude::*, test_constraint_system::TestConstraintSystem,
-    };
+    use crate::{prelude::*, test_constraint_system::TestConstraintSystem};
     use algebra::groups::Group;
     use rand;
 
@@ -203,8 +222,7 @@ mod test {
     #[test]
     fn jubjub_group_gadgets_test() {
         use crate::groups::jubjub::JubJubGadget;
-        use algebra::fields::jubjub::fq::Fq;
-        use algebra::curves::jubjub::JubJubProjective;
+        use algebra::{curves::jubjub::JubJubProjective, fields::jubjub::fq::Fq};
 
         let mut cs = TestConstraintSystem::<Fq>::new();
 

r1cs-std/src/lib.rs

@@ -49,18 +49,20 @@ pub mod groups;
 
 pub mod pairing;
 
+pub mod alloc;
 pub mod eq;
 pub mod select;
-pub mod alloc;
 
 pub mod prelude {
-    pub use crate::eq::*;
-    pub use crate::select::*;
-    pub use crate::alloc::*;
-    pub use crate::fields::FieldGadget;
-    pub use crate::groups::GroupGadget;
-    pub use crate::pairing::PairingGadget;
-    pub use crate::bits::{ToBitsGadget, ToBytesGadget, boolean::Boolean, uint8::UInt8, uint32::UInt32};
+    pub use crate::{
+        alloc::*,
+        bits::{boolean::Boolean, uint32::UInt32, uint8::UInt8, ToBitsGadget, ToBytesGadget},
+        eq::*,
+        fields::FieldGadget,
+        groups::GroupGadget,
+        pairing::PairingGadget,
+        select::*,
+    };
 }
 
 pub trait Assignment<T> {

r1cs-std/src/pairing/mod.rs

@@ -65,14 +65,18 @@ mod test {
     #[test]
     fn bls12_377_gadget_bilinearity_test() {
         use algebra::{
-            fields::{bls12_377::{fr::Fr, fq::Fq}, PrimeField},
+            fields::{
+                bls12_377::{fq::Fq, fr::Fr},
+                PrimeField,
+            },
             PairingEngine, ProjectiveCurve,
         };
 
         use super::bls12_377::PairingGadget;
         use crate::{
             groups::bls12::bls12_377::{G1Gadget, G1PreparedGadget, G2Gadget, G2PreparedGadget},
-            prelude::*, pairing::PairingGadget as _,
+            pairing::PairingGadget as _,
+            prelude::*,
         };
         use algebra::curves::bls12_377::{Bls12_377, G1Projective, G2Projective};
         use std::ops::Mul;

r1cs-std/src/select.rs

@@ -1,7 +1,6 @@
 use crate::prelude::*;
-use r1cs_core::{ConstraintSystem, SynthesisError};
 use algebra::Field;
-
+use r1cs_core::{ConstraintSystem, SynthesisError};
 
 /// If condition is `true`, return `first`; else, select `second`.
 pub trait CondSelectGadget<ConstraintF: Field>
@@ -33,4 +32,19 @@ where
     fn cost() -> usize;
 }
 
+/// Uses three bits to perform a lookup into a table, where the last bit
+/// performs negation
+pub trait ThreeBitCondNegLookupGadget<ConstraintF: Field>
+where
+    Self: Sized,
+{
+    type TableConstant;
+    fn three_bit_cond_neg_lookup<CS: ConstraintSystem<ConstraintF>>(
+        cs: CS,
+        bits: &[Boolean],
+        b0b1: &Boolean,
+        constants: &[Self::TableConstant],
+    ) -> Result<Self, SynthesisError>;
 
+    fn cost() -> usize;
+}