Add group.h ge/gej equality functions

fanquake · Dec 1, 2023 · a47cd97 · a47cd97
1 parent 10e6d29
commit a47cd97
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Showing 3 changed files with 38 additions and 20 deletions.
diff --git a/src/group.h b/src/group.h
@@ -102,6 +102,9 @@ static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a
  */
 static void secp256k1_ge_table_set_globalz(size_t len, secp256k1_ge *a, const secp256k1_fe *zr);
 
+/** Check two group elements (affine) for equality in variable time. */
+static int secp256k1_ge_eq_var(const secp256k1_ge *a, const secp256k1_ge *b);
+
 /** Set a group element (affine) equal to the point at infinity. */
 static void secp256k1_ge_set_infinity(secp256k1_ge *r);
 
@@ -114,6 +117,9 @@ static void secp256k1_gej_set_ge(secp256k1_gej *r, const secp256k1_ge *a);
 /** Check two group elements (jacobian) for equality in variable time. */
 static int secp256k1_gej_eq_var(const secp256k1_gej *a, const secp256k1_gej *b);
 
+/** Check two group elements (jacobian and affine) for equality in variable time. */
+static int secp256k1_gej_eq_ge_var(const secp256k1_gej *a, const secp256k1_ge *b);
+
 /** Compare the X coordinate of a group element (jacobian).
   * The magnitude of the group element's X coordinate must not exceed 31. */
 static int secp256k1_gej_eq_x_var(const secp256k1_fe *x, const secp256k1_gej *a);

diff --git a/src/group_impl.h b/src/group_impl.h
@@ -354,6 +354,35 @@ static int secp256k1_gej_eq_var(const secp256k1_gej *a, const secp256k1_gej *b)
     return secp256k1_gej_is_infinity(&tmp);
 }
 
+static int secp256k1_gej_eq_ge_var(const secp256k1_gej *a, const secp256k1_ge *b) {
+    secp256k1_gej tmp;
+    SECP256K1_GEJ_VERIFY(a);
+    SECP256K1_GE_VERIFY(b);
+
+    secp256k1_gej_neg(&tmp, a);
+    secp256k1_gej_add_ge_var(&tmp, &tmp, b, NULL);
+    return secp256k1_gej_is_infinity(&tmp);
+}
+
+static int secp256k1_ge_eq_var(const secp256k1_ge *a, const secp256k1_ge *b) {
+    secp256k1_fe tmp;
+    SECP256K1_GE_VERIFY(a);
+    SECP256K1_GE_VERIFY(b);
+
+    if (a->infinity != b->infinity) return 0;
+    if (a->infinity) return 1;
+
+    tmp = a->x;
+    secp256k1_fe_normalize_weak(&tmp);
+    if (!secp256k1_fe_equal(&tmp, &b->x)) return 0;
+
+    tmp = a->y;
+    secp256k1_fe_normalize_weak(&tmp);
+    if (!secp256k1_fe_equal(&tmp, &b->y)) return 0;
+
+    return 1;
+}
+
 static int secp256k1_gej_eq_x_var(const secp256k1_fe *x, const secp256k1_gej *a) {
     secp256k1_fe r;
     SECP256K1_FE_VERIFY(x);

diff --git a/src/testutil.h b/src/testutil.h
@@ -7,6 +7,7 @@
 #define SECP256K1_TESTUTIL_H
 
 #include "field.h"
+#include "group.h"
 #include "testrand.h"
 #include "util.h"
 
@@ -27,29 +28,11 @@ static void random_fe_non_zero(secp256k1_fe *nz) {
 }
 
 static void ge_equals_ge(const secp256k1_ge *a, const secp256k1_ge *b) {
-    CHECK(a->infinity == b->infinity);
-    if (a->infinity) {
-        return;
-    }
-    CHECK(secp256k1_fe_equal(&a->x, &b->x));
-    CHECK(secp256k1_fe_equal(&a->y, &b->y));
+    CHECK(secp256k1_ge_eq_var(a, b));
 }
 
 static void ge_equals_gej(const secp256k1_ge *a, const secp256k1_gej *b) {
-    secp256k1_fe z2s;
-    secp256k1_fe u1, u2, s1, s2;
-    CHECK(a->infinity == b->infinity);
-    if (a->infinity) {
-        return;
-    }
-    /* Check a.x * b.z^2 == b.x && a.y * b.z^3 == b.y, to avoid inverses. */
-    secp256k1_fe_sqr(&z2s, &b->z);
-    secp256k1_fe_mul(&u1, &a->x, &z2s);
-    u2 = b->x;
-    secp256k1_fe_mul(&s1, &a->y, &z2s); secp256k1_fe_mul(&s1, &s1, &b->z);
-    s2 = b->y;
-    CHECK(secp256k1_fe_equal(&u1, &u2));
-    CHECK(secp256k1_fe_equal(&s1, &s2));
+    CHECK(secp256k1_gej_eq_ge_var(b, a));
 }
 
 #endif /* SECP256K1_TESTUTIL_H */