stage2 now works; tests pass

1 files changed, 19 insertions, 3 deletions

diff --git a/nizk/stage1.go b/nizk/stage1.go
index ee1be2c..453d683 100644
--- a/nizk/stage1.go
+++ b/nizk/stage1.go
@@ -69,10 +69,26 @@ func (b *Bit) StageFromScalars(x, r *Scalar) (c *StageCommitment) {
 func (b *Bit) reveal(prev_true bool, Xs ...*Point) (r *StageReveal) {
 	s := b.Stage
 
-	// TODO: Calculate Y based on the Xs and our own X_i
+	// Calculate Y based on the Xs and our own X_i
 	// as Π_(i<k) X_k / Π_(i>k) X_k
-	// For now:
-	Y := G
+	// (basically leaving our own X_i out in the calculation).
+	// We are assuming that Xs is ordered already.
+	Y := Curve.Identity()
+	found := false
+	for _, X := range Xs {
+		if !found && X.Equal(b.Stage.X) {
+			found = true
+			continue
+		}
+		if !found {
+			Y = Y.Mul(X)
+		} else {
+			Y = Y.Div(X)
+		}
+	}
+	if !found {
+		panic("own X not found in Xs")
+	}
 
 	r = &StageReveal{Y: Y}