diff --git a/BUILD.gn b/BUILD.gn
index 6e9ef99a574f979a43c5c721054cab73262c0179..52cbe5f6e9c163edeceb003c39154e0751d7104e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1,4 +1,15 @@
-# Copyright (C) Huawei Technologies Co., Ltd. 2020-2020. All rights reserved.
+# Copyright (c) 2020-2022 Huawei Device Co., Ltd.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 import("//build/ohos.gni")
 
diff --git a/crypto/bn/bn_sqrt.c b/crypto/bn/bn_sqrt.c
index 1723d5ded5a87a0d0b665df15678b6013bcce2f7..53b0f559855c10fe5a97ea90f137afe7671ee08f 100644
--- a/crypto/bn/bn_sqrt.c
+++ b/crypto/bn/bn_sqrt.c
@@ -14,7 +14,8 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
 /*
  * Returns 'ret' such that ret^2 == a (mod p), using the Tonelli/Shanks
  * algorithm (cf. Henri Cohen, "A Course in Algebraic Computational Number
- * Theory", algorithm 1.5.1). 'p' must be prime!
+ * Theory", algorithm 1.5.1). 'p' must be prime, otherwise an error or
+ * an incorrect "result" will be returned.
  */
 {
     BIGNUM *ret = in;
@@ -301,18 +302,23 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
             goto vrfy;
         }
 
-        /* find smallest  i  such that  b^(2^i) = 1 */
-        i = 1;
-        if (!BN_mod_sqr(t, b, p, ctx))
-            goto end;
-        while (!BN_is_one(t)) {
-            i++;
-            if (i == e) {
-                BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE);
-                goto end;
+        /* Find the smallest i, 0 < i < e, such that b^(2^i) = 1. */
+        for (i = 1; i < e; i++) {
+            if (i == 1) {
+                if (!BN_mod_sqr(t, b, p, ctx))
+                    goto end;
+
+            } else {
+                if (!BN_mod_mul(t, t, t, p, ctx))
+                    goto end;
             }
-            if (!BN_mod_mul(t, t, t, p, ctx))
-                goto end;
+            if (BN_is_one(t))
+                break;
+        }
+        /* If not found, a is not a square or p is not prime. */
+        if (i >= e) {
+            BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE);
+            goto end;
         }
 
         /* t := y^2^(e - i - 1) */