Move window table lookup logic into its own module.

src/circuit/lookup.rs

@@ -0,0 +1,310 @@
+use pairing::{Engine, Field};
+use super::*;
+use super::num::AllocatedNum;
+use super::boolean::Boolean;
+use bellman::{
+    ConstraintSystem,
+    LinearCombination
+};
+
+// Synthesize the constants for each base pattern.
+fn synth<'a, E: Engine, I>(
+    window_size: usize,
+    constants: I,
+    assignment: &mut [E::Fr]
+)
+    where I: IntoIterator<Item=&'a E::Fr>
+{
+    assert_eq!(assignment.len(), 1 << window_size);
+
+    for (i, constant) in constants.into_iter().enumerate() {
+        let mut cur = assignment[i];
+        cur.negate();
+        cur.add_assign(constant);
+        assignment[i] = cur;
+        for (j, eval) in assignment.iter_mut().enumerate().skip(i + 1) {
+            if j & i == i {
+                eval.add_assign(&cur);
+            }
+        }
+    }
+}
+
+/// Performs a 3-bit window table lookup. `bits` is in
+/// little-endian order.
+pub fn lookup3_xy<E: Engine, CS, Var: Copy>(
+    mut cs: CS,
+    bits: &[Boolean<Var>],
+    coords: &[(E::Fr, E::Fr)]
+) -> Result<(AllocatedNum<E, Var>, AllocatedNum<E, Var>), SynthesisError>
+    where CS: ConstraintSystem<E, Variable=Var>
+{
+    assert_eq!(bits.len(), 3);
+    assert_eq!(coords.len(), 8);
+
+    // Calculate the index into `coords`
+    let i =
+    match (bits[0].get_value(), bits[1].get_value(), bits[2].get_value()) {
+        (Some(a_value), Some(b_value), Some(c_value)) => {
+            let mut tmp = 0;
+            if a_value {
+                tmp += 1;
+            }
+            if b_value {
+                tmp += 2;
+            }
+            if c_value {
+                tmp += 4;
+            }
+            Some(tmp)
+        },
+        _ => None
+    };
+
+    // Allocate the x-coordinate resulting from the lookup
+    let res_x = AllocatedNum::alloc(
+        cs.namespace(|| "x"),
+        || {
+            Ok(coords[*i.get()?].0)
+        }
+    )?;
+
+    // Allocate the y-coordinate resulting from the lookup
+    let res_y = AllocatedNum::alloc(
+        cs.namespace(|| "y"),
+        || {
+            Ok(coords[*i.get()?].1)
+        }
+    )?;
+
+    // Compute the coefficients for the lookup constraints
+    let mut x_coeffs = [E::Fr::zero(); 8];
+    let mut y_coeffs = [E::Fr::zero(); 8];
+    synth::<E, _>(3, coords.iter().map(|c| &c.0), &mut x_coeffs);
+    synth::<E, _>(3, coords.iter().map(|c| &c.1), &mut y_coeffs);
+
+    let precomp = Boolean::and(cs.namespace(|| "precomp"), &bits[1], &bits[2])?;
+
+    let one = cs.one();
+
+    cs.enforce(
+        || "x-coordinate lookup",
+        LinearCombination::<Var, E>::zero() + (x_coeffs[0b001], one)
+                                            + &bits[1].lc::<E>(one, x_coeffs[0b011])
+                                            + &bits[2].lc::<E>(one, x_coeffs[0b101])
+                                            + &precomp.lc::<E>(one, x_coeffs[0b111]),
+        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
+        LinearCombination::<Var, E>::zero() + res_x.get_variable()
+                                            - (x_coeffs[0b000], one)
+                                            - &bits[1].lc::<E>(one, x_coeffs[0b010])
+                                            - &bits[2].lc::<E>(one, x_coeffs[0b100])
+                                            - &precomp.lc::<E>(one, x_coeffs[0b110]),
+    );
+
+    cs.enforce(
+        || "y-coordinate lookup",
+        LinearCombination::<Var, E>::zero() + (y_coeffs[0b001], one)
+                                            + &bits[1].lc::<E>(one, y_coeffs[0b011])
+                                            + &bits[2].lc::<E>(one, y_coeffs[0b101])
+                                            + &precomp.lc::<E>(one, y_coeffs[0b111]),
+        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
+        LinearCombination::<Var, E>::zero() + res_y.get_variable()
+                                            - (y_coeffs[0b000], one)
+                                            - &bits[1].lc::<E>(one, y_coeffs[0b010])
+                                            - &bits[2].lc::<E>(one, y_coeffs[0b100])
+                                            - &precomp.lc::<E>(one, y_coeffs[0b110]),
+    );
+
+    Ok((res_x, res_y))
+}
+
+/// Performs a 3-bit window table lookup, where
+/// one of the bits is a sign bit.
+pub fn lookup3_xy_with_conditional_negation<E: Engine, CS, Var: Copy>(
+    mut cs: CS,
+    bits: &[Boolean<Var>],
+    coords: &[(E::Fr, E::Fr)]
+) -> Result<(AllocatedNum<E, Var>, AllocatedNum<E, Var>), SynthesisError>
+    where CS: ConstraintSystem<E, Variable=Var>
+{
+    assert_eq!(bits.len(), 3);
+    assert_eq!(coords.len(), 4);
+
+    // Calculate the index into `coords`
+    let i =
+    match (bits[0].get_value(), bits[1].get_value()) {
+        (Some(a_value), Some(b_value)) => {
+            let mut tmp = 0;
+            if a_value {
+                tmp += 1;
+            }
+            if b_value {
+                tmp += 2;
+            }
+            Some(tmp)
+        },
+        _ => None
+    };
+
+    // Allocate the x-coordinate resulting from the lookup
+    let res_x = AllocatedNum::alloc(
+        cs.namespace(|| "x"),
+        || {
+            Ok(coords[*i.get()?].0)
+        }
+    )?;
+
+    // Allocate the y-coordinate resulting from the lookup
+    let res_y = AllocatedNum::alloc(
+        cs.namespace(|| "y"),
+        || {
+            Ok(coords[*i.get()?].1)
+        }
+    )?;
+
+    let one = cs.one();
+
+    // Compute the coefficients for the lookup constraints
+    let mut x_coeffs = [E::Fr::zero(); 4];
+    let mut y_coeffs = [E::Fr::zero(); 4];
+    synth::<E, _>(2, coords.iter().map(|c| &c.0), &mut x_coeffs);
+    synth::<E, _>(2, coords.iter().map(|c| &c.1), &mut y_coeffs);
+
+    cs.enforce(
+        || "x-coordinate lookup",
+        LinearCombination::<Var, E>::zero() + (x_coeffs[0b01], one)
+                                            + &bits[1].lc::<E>(one, x_coeffs[0b11]),
+        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
+        LinearCombination::<Var, E>::zero() + res_x.get_variable()
+                                            - (x_coeffs[0b00], one)
+                                            - &bits[1].lc::<E>(one, x_coeffs[0b10])
+    );
+
+    cs.enforce(
+        || "y-coordinate lookup",
+        LinearCombination::<Var, E>::zero() + (y_coeffs[0b01], one)
+                                            + &bits[1].lc::<E>(one, y_coeffs[0b11]),
+        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
+        LinearCombination::<Var, E>::zero() + res_y.get_variable()
+                                            - (y_coeffs[0b00], one)
+                                            - &bits[1].lc::<E>(one, y_coeffs[0b10])
+    );
+
+    let final_y = res_y.conditionally_negate(&mut cs, &bits[2])?;
+
+    Ok((res_x, final_y))
+}
+
+#[cfg(test)]
+mod test {
+    use rand::{SeedableRng, Rand, Rng, XorShiftRng};
+    use super::*;
+    use ::circuit::test::*;
+    use ::circuit::boolean::{Boolean, AllocatedBit};
+    use pairing::bls12_381::{Bls12, Fr};
+
+    #[test]
+    fn test_lookup3_xy() {
+        let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0656]);
+
+        for _ in 0..100 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a_val = rng.gen();
+            let a = Boolean::from(
+                AllocatedBit::alloc(cs.namespace(|| "a"), Some(a_val)).unwrap()
+            );
+
+            let b_val = rng.gen();
+            let b = Boolean::from(
+                AllocatedBit::alloc(cs.namespace(|| "b"), Some(b_val)).unwrap()
+            );
+
+            let c_val = rng.gen();
+            let c = Boolean::from(
+                AllocatedBit::alloc(cs.namespace(|| "c"), Some(c_val)).unwrap()
+            );
+
+            let bits = vec![a, b, c];
+
+            let points: Vec<(Fr, Fr)> = (0..8).map(|_| (rng.gen(), rng.gen())).collect();
+
+            let res = lookup3_xy(&mut cs, &bits, &points).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut index = 0;
+            if a_val { index += 1 }
+            if b_val { index += 2 }
+            if c_val { index += 4 }
+
+            assert_eq!(res.0.get_value().unwrap(), points[index].0);
+            assert_eq!(res.1.get_value().unwrap(), points[index].1);
+        }
+    }
+
+    #[test]
+    fn test_lookup3_xy_with_conditional_negation() {
+        let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
+
+        for _ in 0..100 {
+            let mut cs = TestConstraintSystem::<Bls12>::new();
+
+            let a_val = rng.gen();
+            let a = Boolean::from(
+                AllocatedBit::alloc(cs.namespace(|| "a"), Some(a_val)).unwrap()
+            );
+
+            let b_val = rng.gen();
+            let b = Boolean::from(
+                AllocatedBit::alloc(cs.namespace(|| "b"), Some(b_val)).unwrap()
+            );
+
+            let c_val = rng.gen();
+            let c = Boolean::from(
+                AllocatedBit::alloc(cs.namespace(|| "c"), Some(c_val)).unwrap()
+            );
+
+            let bits = vec![a, b, c];
+
+            let points: Vec<(Fr, Fr)> = (0..4).map(|_| (rng.gen(), rng.gen())).collect();
+
+            let res = lookup3_xy_with_conditional_negation(&mut cs, &bits, &points).unwrap();
+
+            assert!(cs.is_satisfied());
+
+            let mut index = 0;
+            if a_val { index += 1 }
+            if b_val { index += 2 }
+
+            assert_eq!(res.0.get_value().unwrap(), points[index].0);
+            let mut tmp = points[index].1;
+            if c_val { tmp.negate() }
+            assert_eq!(res.1.get_value().unwrap(), tmp);
+        }
+    }
+
+    #[test]
+    fn test_synth() {
+        let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
+
+        let window_size = 4;
+
+        let mut assignment = vec![Fr::zero(); (1 << window_size)];
+        let constants: Vec<_> = (0..(1 << window_size)).map(|_| Fr::rand(&mut rng)).collect();
+
+        synth::<Bls12, _>(window_size, &constants, &mut assignment);
+
+        for b in 0..(1 << window_size) {
+            let mut acc = Fr::zero();
+
+            for j in 0..(1 << window_size) {
+                if j & b == j {
+                    acc.add_assign(&assignment[j]);
+                }
+            }
+
+            assert_eq!(acc, constants[b]);
+        }
+    }
+}

src/circuit/mod.rs

@@ -6,6 +6,7 @@ pub mod uint32;
 pub mod blake2s;
 pub mod num;
 pub mod mont;
+pub mod lookup;
 pub mod pedersen_hash;
 
 use bellman::SynthesisError;

src/circuit/pedersen_hash.rs

@@ -1,39 +1,14 @@
-use pairing::{Engine, Field};
 use super::*;
 use super::mont::{
     MontgomeryPoint,
     EdwardsPoint
 };
-use super::num::AllocatedNum;
 use super::boolean::Boolean;
 use ::jubjub::*;
 use bellman::{
-    ConstraintSystem,
+    ConstraintSystem
-    LinearCombination
 };
-
+use super::lookup::*;
-// Synthesize the constants for each base pattern.
-fn synth<'a, E: Engine, I>(
-    window_size: usize,
-    constants: I,
-    assignment: &mut [E::Fr]
-)
-    where I: IntoIterator<Item=&'a E::Fr>
-{
-    assert_eq!(assignment.len(), 1 << window_size);
-
-    for (i, constant) in constants.into_iter().enumerate() {
-        let mut cur = assignment[i];
-        cur.negate();
-        cur.add_assign(constant);
-        assignment[i] = cur;
-        for (j, eval) in assignment.iter_mut().enumerate().skip(i + 1) {
-            if j & i == i {
-                eval.add_assign(&cur);
-            }
-        }
-    }
-}
 
 pub fn pedersen_hash<E: JubjubEngine, CS, Var: Copy>(
     mut cs: CS,
@@ -124,174 +99,9 @@ pub fn pedersen_hash<E: JubjubEngine, CS, Var: Copy>(
     Ok(edwards_result.unwrap())
 }
 
-/// Performs a 3-bit window table lookup. `bits` is in
-/// little-endian order.
-fn lookup3_xy<E: Engine, CS, Var: Copy>(
-    mut cs: CS,
-    bits: &[Boolean<Var>],
-    coords: &[(E::Fr, E::Fr)]
-) -> Result<(AllocatedNum<E, Var>, AllocatedNum<E, Var>), SynthesisError>
-    where CS: ConstraintSystem<E, Variable=Var>
-{
-    assert_eq!(bits.len(), 3);
-    assert_eq!(coords.len(), 8);
-
-    // Calculate the index into `coords`
-    let i =
-    match (bits[0].get_value(), bits[1].get_value(), bits[2].get_value()) {
-        (Some(a_value), Some(b_value), Some(c_value)) => {
-            let mut tmp = 0;
-            if a_value {
-                tmp += 1;
-            }
-            if b_value {
-                tmp += 2;
-            }
-            if c_value {
-                tmp += 4;
-            }
-            Some(tmp)
-        },
-        _ => None
-    };
-
-    // Allocate the x-coordinate resulting from the lookup
-    let res_x = AllocatedNum::alloc(
-        cs.namespace(|| "x"),
-        || {
-            Ok(coords[*i.get()?].0)
-        }
-    )?;
-
-    // Allocate the y-coordinate resulting from the lookup
-    let res_y = AllocatedNum::alloc(
-        cs.namespace(|| "y"),
-        || {
-            Ok(coords[*i.get()?].1)
-        }
-    )?;
-
-    // Compute the coefficients for the lookup constraints
-    let mut x_coeffs = [E::Fr::zero(); 8];
-    let mut y_coeffs = [E::Fr::zero(); 8];
-    synth::<E, _>(3, coords.iter().map(|c| &c.0), &mut x_coeffs);
-    synth::<E, _>(3, coords.iter().map(|c| &c.1), &mut y_coeffs);
-
-    let precomp = Boolean::and(cs.namespace(|| "precomp"), &bits[1], &bits[2])?;
-
-    let one = cs.one();
-
-    cs.enforce(
-        || "x-coordinate lookup",
-        LinearCombination::<Var, E>::zero() + (x_coeffs[0b001], one)
-                                            + &bits[1].lc::<E>(one, x_coeffs[0b011])
-                                            + &bits[2].lc::<E>(one, x_coeffs[0b101])
-                                            + &precomp.lc::<E>(one, x_coeffs[0b111]),
-        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
-        LinearCombination::<Var, E>::zero() + res_x.get_variable()
-                                            - (x_coeffs[0b000], one)
-                                            - &bits[1].lc::<E>(one, x_coeffs[0b010])
-                                            - &bits[2].lc::<E>(one, x_coeffs[0b100])
-                                            - &precomp.lc::<E>(one, x_coeffs[0b110]),
-    );
-
-    cs.enforce(
-        || "y-coordinate lookup",
-        LinearCombination::<Var, E>::zero() + (y_coeffs[0b001], one)
-                                            + &bits[1].lc::<E>(one, y_coeffs[0b011])
-                                            + &bits[2].lc::<E>(one, y_coeffs[0b101])
-                                            + &precomp.lc::<E>(one, y_coeffs[0b111]),
-        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
-        LinearCombination::<Var, E>::zero() + res_y.get_variable()
-                                            - (y_coeffs[0b000], one)
-                                            - &bits[1].lc::<E>(one, y_coeffs[0b010])
-                                            - &bits[2].lc::<E>(one, y_coeffs[0b100])
-                                            - &precomp.lc::<E>(one, y_coeffs[0b110]),
-    );
-
-    Ok((res_x, res_y))
-}
-
-/// Performs a 3-bit window table lookup, where
-/// one of the bits is a sign bit.
-fn lookup3_xy_with_conditional_negation<E: Engine, CS, Var: Copy>(
-    mut cs: CS,
-    bits: &[Boolean<Var>],
-    coords: &[(E::Fr, E::Fr)]
-) -> Result<(AllocatedNum<E, Var>, AllocatedNum<E, Var>), SynthesisError>
-    where CS: ConstraintSystem<E, Variable=Var>
-{
-    assert_eq!(bits.len(), 3);
-    assert_eq!(coords.len(), 4);
-
-    // Calculate the index into `coords`
-    let i =
-    match (bits[0].get_value(), bits[1].get_value()) {
-        (Some(a_value), Some(b_value)) => {
-            let mut tmp = 0;
-            if a_value {
-                tmp += 1;
-            }
-            if b_value {
-                tmp += 2;
-            }
-            Some(tmp)
-        },
-        _ => None
-    };
-
-    // Allocate the x-coordinate resulting from the lookup
-    let res_x = AllocatedNum::alloc(
-        cs.namespace(|| "x"),
-        || {
-            Ok(coords[*i.get()?].0)
-        }
-    )?;
-
-    // Allocate the y-coordinate resulting from the lookup
-    let res_y = AllocatedNum::alloc(
-        cs.namespace(|| "y"),
-        || {
-            Ok(coords[*i.get()?].1)
-        }
-    )?;
-
-    let one = cs.one();
-
-    // Compute the coefficients for the lookup constraints
-    let mut x_coeffs = [E::Fr::zero(); 4];
-    let mut y_coeffs = [E::Fr::zero(); 4];
-    synth::<E, _>(2, coords.iter().map(|c| &c.0), &mut x_coeffs);
-    synth::<E, _>(2, coords.iter().map(|c| &c.1), &mut y_coeffs);
-
-    cs.enforce(
-        || "x-coordinate lookup",
-        LinearCombination::<Var, E>::zero() + (x_coeffs[0b01], one)
-                                            + &bits[1].lc::<E>(one, x_coeffs[0b11]),
-        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
-        LinearCombination::<Var, E>::zero() + res_x.get_variable()
-                                            - (x_coeffs[0b00], one)
-                                            - &bits[1].lc::<E>(one, x_coeffs[0b10])
-    );
-
-    cs.enforce(
-        || "y-coordinate lookup",
-        LinearCombination::<Var, E>::zero() + (y_coeffs[0b01], one)
-                                            + &bits[1].lc::<E>(one, y_coeffs[0b11]),
-        LinearCombination::<Var, E>::zero() + &bits[0].lc::<E>(one, E::Fr::one()),
-        LinearCombination::<Var, E>::zero() + res_y.get_variable()
-                                            - (y_coeffs[0b00], one)
-                                            - &bits[1].lc::<E>(one, y_coeffs[0b10])
-    );
-
-    let final_y = res_y.conditionally_negate(&mut cs, &bits[2])?;
-
-    Ok((res_x, final_y))
-}
-
 #[cfg(test)]
 mod test {
-    use rand::{SeedableRng, Rand, Rng, XorShiftRng};
+    use rand::{SeedableRng, Rng, XorShiftRng};
     use super::*;
     use ::circuit::test::*;
     use ::circuit::boolean::{Boolean, AllocatedBit};
@@ -357,109 +167,4 @@ mod test {
             }
         }
     }
-
-    #[test]
-    fn test_lookup3_xy() {
-        let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0656]);
-
-        for _ in 0..100 {
-            let mut cs = TestConstraintSystem::<Bls12>::new();
-
-            let a_val = rng.gen();
-            let a = Boolean::from(
-                AllocatedBit::alloc(cs.namespace(|| "a"), Some(a_val)).unwrap()
-            );
-
-            let b_val = rng.gen();
-            let b = Boolean::from(
-                AllocatedBit::alloc(cs.namespace(|| "b"), Some(b_val)).unwrap()
-            );
-
-            let c_val = rng.gen();
-            let c = Boolean::from(
-                AllocatedBit::alloc(cs.namespace(|| "c"), Some(c_val)).unwrap()
-            );
-
-            let bits = vec![a, b, c];
-
-            let points: Vec<(Fr, Fr)> = (0..8).map(|_| (rng.gen(), rng.gen())).collect();
-
-            let res = lookup3_xy(&mut cs, &bits, &points).unwrap();
-
-            assert!(cs.is_satisfied());
-
-            let mut index = 0;
-            if a_val { index += 1 }
-            if b_val { index += 2 }
-            if c_val { index += 4 }
-
-            assert_eq!(res.0.get_value().unwrap(), points[index].0);
-            assert_eq!(res.1.get_value().unwrap(), points[index].1);
-        }
-    }
-
-    #[test]
-    fn test_lookup3_xy_with_conditional_negation() {
-        let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
-
-        for _ in 0..100 {
-            let mut cs = TestConstraintSystem::<Bls12>::new();
-
-            let a_val = rng.gen();
-            let a = Boolean::from(
-                AllocatedBit::alloc(cs.namespace(|| "a"), Some(a_val)).unwrap()
-            );
-
-            let b_val = rng.gen();
-            let b = Boolean::from(
-                AllocatedBit::alloc(cs.namespace(|| "b"), Some(b_val)).unwrap()
-            );
-
-            let c_val = rng.gen();
-            let c = Boolean::from(
-                AllocatedBit::alloc(cs.namespace(|| "c"), Some(c_val)).unwrap()
-            );
-
-            let bits = vec![a, b, c];
-
-            let points: Vec<(Fr, Fr)> = (0..4).map(|_| (rng.gen(), rng.gen())).collect();
-
-            let res = lookup3_xy_with_conditional_negation(&mut cs, &bits, &points).unwrap();
-
-            assert!(cs.is_satisfied());
-
-            let mut index = 0;
-            if a_val { index += 1 }
-            if b_val { index += 2 }
-
-            assert_eq!(res.0.get_value().unwrap(), points[index].0);
-            let mut tmp = points[index].1;
-            if c_val { tmp.negate() }
-            assert_eq!(res.1.get_value().unwrap(), tmp);
-        }
-    }
-
-    #[test]
-    fn test_synth() {
-        let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
-
-        let window_size = 4;
-
-        let mut assignment = vec![Fr::zero(); (1 << window_size)];
-        let constants: Vec<_> = (0..(1 << window_size)).map(|_| Fr::rand(&mut rng)).collect();
-
-        synth::<Bls12, _>(window_size, &constants, &mut assignment);
-
-        for b in 0..(1 << window_size) {
-            let mut acc = Fr::zero();
-
-            for j in 0..(1 << window_size) {
-                if j & b == j {
-                    acc.add_assign(&assignment[j]);
-                }
-            }
-
-            assert_eq!(acc, constants[b]);
-        }
-    }
 }