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40 lines
1.5 KiB
Rust
40 lines
1.5 KiB
Rust
use ciphersuite::{group::ff::Field, Ciphersuite};
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use crate::*;
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impl<C: Ciphersuite> Circuit<C> {
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/// Constrain two linear combinations to be equal.
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pub fn equality(&mut self, a: LinComb<C::F>, b: &LinComb<C::F>) {
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self.constrain_equal_to_zero(a - b);
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}
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/// Calculate (and constrain) the inverse of a value.
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///
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/// A linear combination may optionally be passed as a constraint for the value being inverted.
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/// A reference to the inverted value and its inverse is returned.
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///
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/// May panic if any linear combinations reference non-existent terms, the witness isn't provided
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/// when proving/is provided when verifying, or if the witness is 0 (and accordingly doesn't have
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/// an inverse).
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pub fn inverse(
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&mut self,
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lincomb: Option<LinComb<C::F>>,
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witness: Option<C::F>,
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) -> (Variable, Variable) {
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let (l, r, o) = self.mul(lincomb, None, witness.map(|f| (f, f.invert().unwrap())));
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// The output of a value multiplied by its inverse is 1
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// Constrain `1 o - 1 = 0`
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self.constrain_equal_to_zero(LinComb::from(o).constant(-C::F::ONE));
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(l, r)
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}
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/// Constrain two linear combinations as inequal.
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///
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/// May panic if any linear combinations reference non-existent terms.
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pub fn inequality(&mut self, a: LinComb<C::F>, b: &LinComb<C::F>, witness: Option<(C::F, C::F)>) {
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let l_constraint = a - b;
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// The existence of a multiplicative inverse means a-b != 0, which means a != b
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self.inverse(Some(l_constraint), witness.map(|(a, b)| a - b));
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}
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}
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