diff --git a/account/decorators.py b/account/decorators.py
index 08aaa811..0b6f236d 100644
--- a/account/decorators.py
+++ b/account/decorators.py
@@ -1,7 +1,11 @@
 import functools
+import hashlib
+import time
+
 from problem.models import Problem
 from contest.models import Contest, ContestType, ContestStatus, ContestRuleType
 from utils.api import JSONResponse, APIError
+from utils.constants import CONTEST_PASSWORD_SESSION_KEY
 from .models import ProblemPermission
 
 
@@ -55,6 +59,32 @@ class problem_permission_required(admin_role_required):
         return True
 
 
+def check_contest_password(password, contest_password):
+    if not (password and contest_password):
+        return False
+    if password == contest_password:
+        return True
+    else:
+        # sig#timestamp 这种形式的密码也可以，但是在界面上没提供支持
+        # sig = sha256(contest_password + timestamp)[:8]
+        if "#" in password:
+            s = password.split("#")
+            if len(s) != 2:
+                return False
+            sig, ts = s[0], s[1]
+
+            if sig == hashlib.sha256((contest_password + ts).encode("utf-8")).hexdigest()[:8]:
+                try:
+                    ts = int(ts)
+                except Exception:
+                    return False
+                return int(time.time()) < ts
+            else:
+                return False
+        else:
+            return False
+
+
 def check_contest_permission(check_type="details"):
     """
     只供Class based view 使用，检查用户是否有权进入该contest, check_type 可选 details, problems, ranks, submissions
@@ -89,8 +119,8 @@ def check_contest_permission(check_type="details"):
 
             if self.contest.contest_type == ContestType.PASSWORD_PROTECTED_CONTEST:
                 # password error
-                if self.contest.id not in request.session.get("accessible_contests", []):
-                    return self.error("Password is required.")
+                if not check_contest_password(request.session.get(CONTEST_PASSWORD_SESSION_KEY, {}).get(self.contest.id), self.contest.password):
+                    return self.error("Wrong password or password expired")
 
             # regular user get contest problems, ranks etc. before contest started
             if self.contest.status == ContestStatus.CONTEST_NOT_START and check_type != "details":
diff --git a/contest/views/oj.py b/contest/views/oj.py
index 3aeb6810..4164ec33 100644
--- a/contest/views/oj.py
+++ b/contest/views/oj.py
@@ -7,10 +7,10 @@ from django.core.cache import cache
 
 from problem.models import Problem
 from utils.api import APIView, validate_serializer
-from utils.constants import CacheKey
+from utils.constants import CacheKey, CONTEST_PASSWORD_SESSION_KEY
 from utils.shortcuts import datetime2str, check_is_id
 from account.models import AdminType
-from account.decorators import login_required, check_contest_permission
+from account.decorators import login_required, check_contest_permission, check_contest_password
 
 from utils.constants import ContestRuleType, ContestStatus
 from ..models import ContestAnnouncement, Contest, OIContestRank, ACMContestRank
@@ -76,13 +76,13 @@ class ContestPasswordVerifyAPI(APIView):
             contest = Contest.objects.get(id=data["contest_id"], visible=True, password__isnull=False)
         except Contest.DoesNotExist:
             return self.error("Contest does not exist")
-        if contest.password != data["password"]:
-            return self.error("Wrong password")
+        if not check_contest_password(data["password"], contest.password):
+            return self.error("Wrong password or password expired")
 
         # password verify OK.
-        if "accessible_contests" not in request.session:
-            request.session["accessible_contests"] = []
-        request.session["accessible_contests"].append(contest.id)
+        if CONTEST_PASSWORD_SESSION_KEY not in request.session:
+            request.session[CONTEST_PASSWORD_SESSION_KEY] = {}
+        request.session[CONTEST_PASSWORD_SESSION_KEY][contest.id] = data["password"]
         # https://docs.djangoproject.com/en/dev/topics/http/sessions/#when-sessions-are-saved
         request.session.modified = True
         return self.success(True)
@@ -94,7 +94,12 @@ class ContestAccessAPI(APIView):
         contest_id = request.GET.get("contest_id")
         if not contest_id:
             return self.error()
-        return self.success({"access": int(contest_id) in request.session.get("accessible_contests", [])})
+        try:
+            contest = Contest.objects.get(id=contest_id, visible=True, password__isnull=False)
+        except Contest.DoesNotExist:
+            return self.error("Contest does not exist")
+        session_pass = request.session.get(CONTEST_PASSWORD_SESSION_KEY, {}).get(contest.id)
+        return self.success({"access": check_contest_password(session_pass, contest.password)})
 
 
 class ContestRankAPI(APIView):
diff --git a/utils/constants.py b/utils/constants.py
index 004b8013..ac0c97b6 100644
--- a/utils/constants.py
+++ b/utils/constants.py
@@ -31,3 +31,6 @@ class Difficulty(Choices):
     LOW = "Low"
     MID = "Mid"
     HIGH = "High"
+
+
+CONTEST_PASSWORD_SESSION_KEY = "contest_password"
\ No newline at end of file