Throw an error when inverse by 0 in BatchCompressTorus() (#222)

* fix: throw an error when inverse by 0 in BatchCompressTorus * fix(bls24-317): throw an error when inverse by 0 in BatchCompressTorus * docs: prettify doc Co-authored-by: Gautam Botrel <gautam.botrel@gmail.com>
Consensys · Jul 27, 2022 · 910b0ec · 910b0ec
1 parent c94b731
commit 910b0ec
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Showing 10 changed files with 60 additions and 15 deletions.
diff --git a/ecc/bls12-377/internal/fptower/e12.go b/ecc/bls12-377/internal/fptower/e12.go
diff --git a/ecc/bls12-378/internal/fptower/e12.go b/ecc/bls12-378/internal/fptower/e12.go
diff --git a/ecc/bls12-381/internal/fptower/e12.go b/ecc/bls12-381/internal/fptower/e12.go
diff --git a/ecc/bls24-315/internal/fptower/e24.go b/ecc/bls24-315/internal/fptower/e24.go
diff --git a/ecc/bls24-317/internal/fptower/e24.go b/ecc/bls24-317/internal/fptower/e24.go
diff --git a/ecc/bn254/internal/fptower/e12.go b/ecc/bn254/internal/fptower/e12.go
diff --git a/ecc/bw6-633/internal/fptower/e6.go b/ecc/bw6-633/internal/fptower/e6.go
diff --git a/ecc/bw6-756/internal/fptower/e6.go b/ecc/bw6-756/internal/fptower/e6.go
diff --git a/ecc/bw6-761/internal/fptower/e6.go b/ecc/bw6-761/internal/fptower/e6.go
diff --git a/internal/generator/tower/template/fq12over6over2/fq12.go.tmpl b/internal/generator/tower/template/fq12over6over2/fq12.go.tmpl
@@ -793,13 +793,14 @@ func (z *E12) CompressTorus() (E6, error) {
 	return res, nil
 }
 
-// BatchCompressTorus GT/E12 elements to half their size
-// using a batch inversion
+// BatchCompressTorus GT/E12 elements to half their size using a batch inversion.
+// 
+// if len(x) == 0 or if any of the x[i].C1 coordinate is 0, this function returns an error.
 func BatchCompressTorus(x []E12) ([]E6, error) {
 
 	n := len(x)
 	if n == 0 {
-		return []E6{}, errors.New("invalid input size")
+		return nil, errors.New("invalid input size")
 	}
 
 	var one E6
@@ -808,6 +809,10 @@ func BatchCompressTorus(x []E12) ([]E6, error) {
 
 	for i := 0; i < n; i++ {
 		res[i].Set(&x[i].C1)
+		//  throw an error if any of the x[i].C1 is 0
+		if res[i].IsZero() {
+			return nil, errors.New("invalid input; C1 is 0")
+		}
 	}
 
 	t := BatchInvertE6(res) // costs 1 inverse