diff --git a/seahub/api2/endpoints/user.py b/seahub/api2/endpoints/user.py
index df6748d3ec..47af1c9c35 100644
--- a/seahub/api2/endpoints/user.py
+++ b/seahub/api2/endpoints/user.py
@@ -252,7 +252,7 @@ class ResetPasswordView(APIView):
         user.save()
 
         if not request.session.is_empty():
-            # update session auth hash
+            # invalidate all active sessions after change password.
             update_session_auth_hash(request, request.user)
 
         return Response({'success': True})
diff --git a/seahub/auth/models.py b/seahub/auth/models.py
index 9ae0026a61..883ae141d1 100644
--- a/seahub/auth/models.py
+++ b/seahub/auth/models.py
@@ -1,46 +1,15 @@
 # Copyright (c) 2012-2016 Seafile Ltd.
-import hashlib
 import logging
 from registration.signals import user_deleted
 from django.db import models
 from django.conf import settings
 from django.dispatch import receiver
-from django.utils.encoding import smart_str
 from django.db.models.manager import EmptyManager
 
 logger = logging.getLogger(__name__)
 UNUSABLE_PASSWORD = '!'  # This will never be a valid hash
 
 
-def get_hexdigest(algorithm, salt, raw_password):
-    """
-    Returns a string of the hexdigest of the given plaintext password and salt
-    using the given algorithm ('md5', 'sha1' or 'crypt').
-    """
-    raw_password, salt = smart_str(raw_password).encode('utf-8'), smart_str(salt).encode('utf-8')
-    if algorithm == 'crypt':
-        try:
-            import crypt
-        except ImportError:
-            raise ValueError('"crypt" password algorithm not supported in this environment')
-        return crypt.crypt(raw_password, salt)
-
-    if algorithm == 'md5':
-        return hashlib.md5(salt + raw_password).hexdigest()
-    elif algorithm == 'sha1':
-        return hashlib.sha1(salt + raw_password).hexdigest()
-    raise ValueError("Got unknown password algorithm type in password.")
-
-
-def check_password(raw_password, enc_password):
-    """
-    Returns a boolean of whether the raw_password was correct. Handles
-    encryption formats behind the scenes.
-    """
-    algo, salt, hsh = enc_password.split('$')
-    return hsh == get_hexdigest(algo, salt, raw_password)
-
-
 class SiteProfileNotAvailable(Exception):
     pass
 
diff --git a/seahub/base/accounts.py b/seahub/base/accounts.py
index 5c3f4f5f2f..711049f10c 100644
--- a/seahub/base/accounts.py
+++ b/seahub/base/accounts.py
@@ -670,13 +670,6 @@ class User(object):
         Returns a boolean of whether the raw_password was correct. Handles
         encryption formats behind the scenes.
         """
-        # Backwards-compatibility check. Older passwords won't include the
-        # algorithm or salt.
-
-        # if '$' not in self.password:
-        #     is_correct = (self.password == \
-        #                       get_hexdigest('sha1', '', raw_password))
-        #     return is_correct
         return (ccnet_threaded_rpc.validate_emailuser(self.username, raw_password) == 0)
 
     def set_unusable_password(self):
diff --git a/seahub/password_session/handlers.py b/seahub/password_session/handlers.py
index 48a436810e..8dbb11fbee 100644
--- a/seahub/password_session/handlers.py
+++ b/seahub/password_session/handlers.py
@@ -11,6 +11,9 @@ PASSWORD_HASH_KEY = getattr(settings, 'PASSWORD_SESSION_PASSWORD_HASH_KEY', 'pas
 def get_password_hash(user):
     """Returns a string of crypted password hash"""
     password = user.enc_password or ''
+    # To achieve "invalidate all active sessions after change password",
+    # a hash value generated based on the user password is stored in the session,
+    # and compare it for each request in the MIDDLEWARE.
     return md5(
         md5(password.encode()).hexdigest().encode() + settings.SECRET_KEY.encode()
     ).hexdigest()
diff --git a/thirdpart/registration/models.py b/thirdpart/registration/models.py
index 6d674a5787..371496baf3 100644
--- a/thirdpart/registration/models.py
+++ b/thirdpart/registration/models.py
@@ -115,7 +115,10 @@ class RegistrationManager(models.Manager):
         username = user.username
         if isinstance(username, str):
             username = username.encode('utf-8')
-        activation_key = hashlib.sha1(salt+username).hexdigest()
+
+        # Take the first 16 character to avoid errors.
+        # (1406, "Data too long for column 'activation_key' at row 1")
+        activation_key = hashlib.sha256(salt+username).hexdigest()[:16]
         return self.create(emailuser_id=user.id,
                            activation_key=activation_key)
         
diff --git a/tools/seahub-admin.py b/tools/seahub-admin.py
deleted file mode 100644
index e5852c43a9..0000000000
--- a/tools/seahub-admin.py
+++ /dev/null
@@ -1,91 +0,0 @@
-#!/usr/bin/env python
-# encoding: utf-8
-# Copyright (c) 2012-2016 Seafile Ltd.
-
-import sqlite3
-import os
-import sys
-import time
-import hashlib
-import getpass
-
-# Get .ccnet directory from argument or user input
-if len(sys.argv) >= 2:
-    ccnet_dir = sys.argv[1]
-else:    
-    home_dir = os.path.join(os.path.expanduser('~'), '.ccnet')
-    ccnet_dir = input("Enter ccnet directory:(leave blank for %s) " % home_dir)
-    if not ccnet_dir:
-        ccnet_dir = home_dir
-
-# Test usermgr.db exists
-usermgr_db = os.path.join(ccnet_dir, 'PeerMgr/usermgr.db')
-if not os.path.exists(usermgr_db):
-    print('%s DOES NOT exist. FAILED' % usermgr_db)
-    sys.exit(1)
-
-# Connect db
-conn = sqlite3.connect(usermgr_db)
-
-# Get cursor
-c = conn.cursor()
-
-# Check whether admin user exists
-sql = "SELECT email FROM EmailUser WHERE is_staff = 1"
-try:
-    c.execute(sql)
-except sqlite3.Error as e:
-    print("An error orrured:", e.args[0])
-    sys.exit(1)
-
-staff_list = c.fetchall()
-if staff_list:
-    print("Admin is already in database. Email as follows: ")
-    print('--------------------')
-    for e in staff_list:
-        print(e[0])
-    print('--------------------')
-    choice = input('Previous admin would be deleted, would you like to continue?[y/n] ')
-    if choice == 'y':
-        sql = "DELETE FROM EmailUser WHERE is_staff = 1"
-        try:
-            c.execute(sql)
-        except sqlite3.Error as e:
-            print("An error orrured:", e.args[0])
-            sys.exit(1)
-        else:
-            print('Previous admin is deleted.')
-    else:
-        conn.close()
-        sys.exit(0)
-
-# Create admin user
-choice = input('Would you like to create admin user?[y/n]')
-if choice != 'y':
-    conn.close()
-    sys.exit(0)
-
-username = input('E-mail address:')
-passwd = getpass.getpass('Password:')
-passwd2 = getpass.getpass('Password (again):')
-if passwd != passwd2:
-    print("Two passwords NOT same.")
-    sys.exit(1)
-    
-mySha1 = hashlib.sha1()
-mySha1.update(passwd.encode('utf-8'))
-enc_passwd = mySha1.hexdigest()
-sql = "INSERT INTO EmailUser(email, passwd, is_staff, is_active, ctime) VALUES ('%s', '%s', 1, 1, '%d');" % (username, enc_passwd, time.time()*1000000)
-try:
-    c = conn.cursor()
-    c.execute(sql)
-    conn.commit()
-except sqlite3.Error as e:
-    print("An error occured:", e.args[0])
-    sys.exit(1)
-else:
-    print("Admin user created successfully.")
-    
-# Close db    
-conn.close()
-