Fix is_zero for twisted Edwards curves (#101)

* fix the te is_zero

* update CHANGELOG

Co-authored-by: onewayfunc <[email protected]>

Author: weikengchen

.github/workflows/ci.yml

@@ -186,6 +186,7 @@ jobs:
             echo "ark-ec = { git = 'https://github.com/arkworks-rs/algebra' }"
             echo "ark-ff = { git = 'https://github.com/arkworks-rs/algebra' }"
             echo "ark-poly = { git = 'https://github.com/arkworks-rs/algebra' }"
+            echo "ark-relations = { git = 'https://github.com/arkworks-rs/snark' }"
             echo "ark-serialize = { git = 'https://github.com/arkworks-rs/algebra' }"
             echo "ark-algebra-bench-templates = { git = 'https://github.com/arkworks-rs/algebra' }"
             echo "ark-algebra-test-templates = { git = 'https://github.com/arkworks-rs/algebra' }"

CHANGELOG.md

@@ -18,6 +18,7 @@
 
 ### Bug Fixes
 
+- [\#101](https://github.com/arkworks-rs/r1cs-std/pull/101) Fix `is_zero` for twisted Edwards curves.
 - [\#86](https://github.com/arkworks-rs/r1cs-std/pull/86) Make result of `query_position_to_coset` consistent with `ark-ldt`.
 - [\#77](https://github.com/arkworks-rs/r1cs-std/pull/77) Fix BLS12 `G2PreparedGadget`'s `AllocVar` when G2 uses a divisive twist.
 

src/groups/curves/twisted_edwards/mod.rs

@@ -423,7 +423,7 @@ where
     }
 
     fn is_zero(&self) -> Result<Boolean<<P::BaseField as Field>::BasePrimeField>, SynthesisError> {
-        self.x.is_zero()?.and(&self.x.is_one()?)
+        self.x.is_zero()?.and(&self.y.is_one()?)
     }
 
     #[tracing::instrument(target = "r1cs", skip(cs, f))]