Implement GroupElement.equals() properly

Author: str4d

src/net/i2p/crypto/eddsa/math/GroupElement.java

@@ -389,13 +389,35 @@ public boolean equals(Object obj) {
                 return false;
             }
         }
-        FieldElement recip1 = Z.invert();
-        FieldElement x1 = X.multiply(recip1);
-        FieldElement y1 = Y.multiply(recip1);
-        FieldElement recip2 = ge.Z.invert();
-        FieldElement x2 = ge.X.multiply(recip2);
-        FieldElement y2 = ge.Y.multiply(recip2);
-        return x1.equals(x2) && y1.equals(y2);
+        switch (this.repr) {
+        case P2:
+        case P3:
+            FieldElement recip1 = Z.invert();
+            FieldElement x1 = X.multiply(recip1);
+            FieldElement y1 = Y.multiply(recip1);
+            FieldElement recip2 = ge.Z.invert();
+            FieldElement x2 = ge.X.multiply(recip2);
+            FieldElement y2 = ge.Y.multiply(recip2);
+            return x1.equals(x2) && y1.equals(y2);
+        case P1P1:
+            return toP2().equals(ge);
+        case PRECOMP:
+            // Compare directly, PRECOMP is derived directly from x and y
+            return X.equals(ge.X) && Y.equals(ge.Y) && Z.equals(ge.Z);
+        case CACHED:
+            // (Y+X)/Z = y+x etc.
+            FieldElement recip3 = Z.invert();
+            FieldElement x3 = X.multiply(recip3);
+            FieldElement y3 = Y.multiply(recip3);
+            FieldElement t3 = T.multiply(recip3);
+            FieldElement recip4 = ge.Z.invert();
+            FieldElement x4 = ge.X.multiply(recip4);
+            FieldElement y4 = ge.Y.multiply(recip4);
+            FieldElement t4 = ge.T.multiply(recip4);
+            return x3.equals(x4) && y3.equals(y4) && t3.equals(t4);
+        default:
+            return false;
+        }
     }
 
     /**