Abstract out verify logic for fe_is_square_var

bitcoin-core · May 11, 2023 · 44eb1d8 · 44eb1d8
1 parent 3f1b689
commit 44eb1d8
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Showing 4 changed files with 14 additions and 10 deletions.
diff --git a/src/field.h b/src/field.h
@@ -100,6 +100,7 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
 #  define secp256k1_fe_get_bounds secp256k1_fe_impl_get_bounds
 #  define secp256k1_fe_half secp256k1_fe_impl_half
 #  define secp256k1_fe_add_int secp256k1_fe_impl_add_int
+#  define secp256k1_fe_is_square_var secp256k1_fe_impl_is_square_var
 #endif /* !defined(VERIFY) */
 
 /** Normalize a field element.

diff --git a/src/field_10x26_impl.h b/src/field_10x26_impl.h
@@ -1215,7 +1215,7 @@ static void secp256k1_fe_impl_inv_var(secp256k1_fe *r, const secp256k1_fe *x) {
     secp256k1_fe_from_signed30(r, &s);
 }
 
-static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
+static int secp256k1_fe_impl_is_square_var(const secp256k1_fe *x) {
     secp256k1_fe tmp;
     secp256k1_modinv32_signed30 s;
     int jac, ret;
@@ -1233,10 +1233,6 @@ static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
         secp256k1_fe dummy;
         ret = secp256k1_fe_sqrt(&dummy, &tmp);
     } else {
-#ifdef VERIFY
-        secp256k1_fe dummy;
-        VERIFY_CHECK(jac == 2*secp256k1_fe_sqrt(&dummy, &tmp) - 1);
-#endif
         ret = jac >= 0;
     }
     return ret;

diff --git a/src/field_5x52_impl.h b/src/field_5x52_impl.h
@@ -504,7 +504,7 @@ static void secp256k1_fe_impl_inv_var(secp256k1_fe *r, const secp256k1_fe *x) {
     secp256k1_fe_from_signed62(r, &s);
 }
 
-static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
+static int secp256k1_fe_impl_is_square_var(const secp256k1_fe *x) {
     secp256k1_fe tmp;
     secp256k1_modinv64_signed62 s;
     int jac, ret;
@@ -522,10 +522,6 @@ static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
         secp256k1_fe dummy;
         ret = secp256k1_fe_sqrt(&dummy, &tmp);
     } else {
-#ifdef VERIFY
-        secp256k1_fe dummy;
-        VERIFY_CHECK(jac == 2*secp256k1_fe_sqrt(&dummy, &tmp) - 1);
-#endif
         ret = jac >= 0;
     }
     return ret;

diff --git a/src/field_impl.h b/src/field_impl.h
@@ -375,6 +375,17 @@ SECP256K1_INLINE static void secp256k1_fe_inv_var(secp256k1_fe *r, const secp256
     secp256k1_fe_verify(r);
 }
 
+static int secp256k1_fe_impl_is_square_var(const secp256k1_fe *x);
+SECP256K1_INLINE static int secp256k1_fe_is_square_var(const secp256k1_fe *x) {
+    int ret;
+    secp256k1_fe tmp = *x, sqrt;
+    secp256k1_fe_verify(x);
+    ret = secp256k1_fe_impl_is_square_var(x);
+    secp256k1_fe_normalize_weak(&tmp);
+    VERIFY_CHECK(ret == secp256k1_fe_sqrt(&sqrt, &tmp));
+    return ret;
+}
+
 static void secp256k1_fe_impl_get_bounds(secp256k1_fe* r, int m);
 SECP256K1_INLINE static void secp256k1_fe_get_bounds(secp256k1_fe* r, int m) {
     VERIFY_CHECK(m >= 0);