diff --git a/src/controllers/noteController.js b/src/controllers/noteController.js
index ff7322f..df3e855 100644
--- a/src/controllers/noteController.js
+++ b/src/controllers/noteController.js
@@ -31,14 +31,14 @@ const updateNote = async (req, res) => {
     const { title, description } = req.body;
 
     try {
-        const updatedNote = await noteModel.findByIdAndUpdate(
-            noteId,
-            { title: title, description: description, userId: req.userId },
+        const updatedNote = await noteModel.findOneAndUpdate(
+            { _id: noteId, userId: req.userId },
+            { title: title, description: description },
             { new: true, runValidators: true }
         );
 
         if (!updatedNote) {
-            return res.status(404).json({ message: "Note not found" });
+            return res.status(404).json({ message: "Note not found or unauthorized" });
         }
 
         res.status(200).json(updatedNote);
@@ -55,10 +55,13 @@ const deleteNote = async (req, res) => {
     const noteId = req.params.noteId;
 
     try {
-        const deletedNote = await noteModel.findOneAndDelete({ _id: noteId });
+        const deletedNote = await noteModel.findOneAndDelete({ 
+            _id: noteId, 
+            userId: req.userId 
+        });
 
         if (!deletedNote) {
-            return res.status(404).json({ message: "Note not found" });
+            return res.status(404).json({ message: "Note not found or unauthorized" });
         }
 
         res.status(202).json(deletedNote);
diff --git a/src/middlewares/auth.js b/src/middlewares/auth.js
index 7fb6794..849d332 100644
--- a/src/middlewares/auth.js
+++ b/src/middlewares/auth.js
@@ -1,36 +1,48 @@
 
 const jwt = require('jsonwebtoken');
-const { use } = require('../routes/userRoutes');
 
 const SECRET_KEY = process.env.SECRET_KEY;
 
-const auth = (req, res, next) => {
-
+if (!SECRET_KEY) {
+    console.error('SECRET_KEY is not set in environment variables');
+    process.exit(1);
+}
 
+const auth = (req, res, next) => {
     try {
-        let token = req.headers.authorization;
-        if (token) {
-            token = token.split(" ")[1];
+        const authHeader = req.headers.authorization;
+        
+        if (!authHeader) {
+            return res.status(401).json({ message: "Authorization header is required" });
+        }
 
-            let user = jwt.verify(token, SECRET_KEY);
+        if (!authHeader.startsWith('Bearer ')) {
+            return res.status(401).json({ message: "Invalid authorization format. Use 'Bearer <token>'" });
+        }
 
-            req.userId = user.id;
+        const token = authHeader.split(" ")[1];
+        const user = jwt.verify(token, SECRET_KEY);
 
-        }
-        else {
-            return res.status(401).json({ message: "You are not logged in" })
+        if (!user.id) {
+            return res.status(401).json({ message: "Invalid token: missing user ID" });
         }
 
+        req.userId = user.id;
         next();
 
     } catch (error) {
         console.log(error);
-        res.status(401).json({ message: "You are not logged in" })
+        
+        if (error.name === 'JsonWebTokenError') {
+            return res.status(401).json({ message: "Invalid token" });
+        }
+        
+        if (error.name === 'TokenExpiredError') {
+            return res.status(401).json({ message: "Token has expired" });
+        }
 
+        res.status(401).json({ message: "You are not logged in" });
     }
-
-
-
 }
 
 module.exports = auth;
\ No newline at end of file
diff --git a/test-authz.js b/test-authz.js
new file mode 100644
index 0000000..6f904f5
--- /dev/null
+++ b/test-authz.js
@@ -0,0 +1,209 @@
+
+const http = require('http');
+
+const BASE_URL = 'http://localhost:5000';
+
+async function makeRequest(options, body = null) {
+    return new Promise((resolve, reject) => {
+        const req = http.request(options, (res) => {
+            let data = '';
+            res.on('data', chunk => data += chunk);
+            res.on('end', () => {
+                try {
+                    const response = {
+                        statusCode: res.statusCode,
+                        headers: res.headers,
+                        body: data ? JSON.parse(data) : null
+                    };
+                    resolve(response);
+                } catch (e) {
+                    reject(e);
+                }
+            });
+        });
+
+        req.on('error', reject);
+
+        if (body) {
+            req.write(JSON.stringify(body));
+        }
+
+        req.end();
+    });
+}
+
+async function registerUser(username, email, password) {
+    const options = {
+        hostname: 'localhost',
+        port: 5000,
+        path: '/users/signup',
+        method: 'POST',
+        headers: {
+            'Content-Type': 'application/json'
+        }
+    };
+
+    const response = await makeRequest(options, { username, email, password });
+    return response;
+}
+
+async function createNote(token, title, description) {
+    const options = {
+        hostname: 'localhost',
+        port: 5000,
+        path: '/notes',
+        method: 'POST',
+        headers: {
+            'Content-Type': 'application/json',
+            'Authorization': `Bearer ${token}`
+        }
+    };
+
+    const response = await makeRequest(options, { title, description });
+    return response;
+}
+
+async function updateNote(token, noteId, title, description) {
+    const options = {
+        hostname: 'localhost',
+        port: 5000,
+        path: `/notes/${noteId}`,
+        method: 'PUT',
+        headers: {
+            'Content-Type': 'application/json',
+            'Authorization': `Bearer ${token}`
+        }
+    };
+
+    const response = await makeRequest(options, { title, description });
+    return response;
+}
+
+async function deleteNote(token, noteId) {
+    const options = {
+        hostname: 'localhost',
+        port: 5000,
+        path: `/notes/${noteId}`,
+        method: 'DELETE',
+        headers: {
+            'Authorization': `Bearer ${token}`
+        }
+    };
+
+    const response = await makeRequest(options);
+    return response;
+}
+
+async function runTests() {
+    console.log('========================================');
+    console.log('  权限控制测试: 用户A vs 用户B');
+    console.log('========================================\n');
+
+    try {
+        // 1. 注册用户A
+        console.log('1. 注册用户A (userA@test.com)');
+        const userAResponse = await registerUser('userA', 'userA@test.com', 'password123');
+        console.log(`   状态码: ${userAResponse.statusCode}`);
+        if (userAResponse.statusCode !== 201) {
+            console.log(`   消息: ${userAResponse.body?.message}`);
+            console.log('\n提示: 请确保服务器已启动 (npm start) 并且 MongoDB 正在运行');
+            process.exit(1);
+        }
+        const userAToken = userAResponse.body.token;
+        const userAId = userAResponse.body.user._id;
+        console.log(`   用户ID: ${userAId}`);
+        console.log('   ✓ 用户A注册成功\n');
+
+        // 2. 注册用户B
+        console.log('2. 注册用户B (userB@test.com)');
+        const userBResponse = await registerUser('userB', 'userB@test.com', 'password123');
+        console.log(`   状态码: ${userBResponse.statusCode}`);
+        const userBToken = userBResponse.body.token;
+        const userBId = userBResponse.body.user._id;
+        console.log(`   用户ID: ${userBId}`);
+        console.log('   ✓ 用户B注册成功\n');
+
+        // 3. 用户A创建笔记
+        console.log('3. 用户A创建笔记');
+        const noteResponse = await createNote(userAToken, '用户A的私人笔记', '这是只有用户A才能访问的笔记内容');
+        console.log(`   状态码: ${noteResponse.statusCode}`);
+        const noteId = noteResponse.body._id;
+        const noteUserId = noteResponse.body.userId;
+        console.log(`   笔记ID: ${noteId}`);
+        console.log(`   笔记所属用户ID: ${noteUserId}`);
+        console.log('   ✓ 用户A创建笔记成功\n');
+
+        // 4. 验证用户B不能更新用户A的笔记
+        console.log('4. 测试权限控制: 用户B尝试更新用户A的笔记');
+        const updateByBResponse = await updateNote(userBToken, noteId, '被用户B修改的标题', '被用户B修改的内容');
+        console.log(`   状态码: ${updateByBResponse.statusCode}`);
+        console.log(`   返回消息: ${updateByBResponse.body?.message}`);
+        
+        if (updateByBResponse.statusCode === 404 && 
+            updateByBResponse.body?.message === "Note not found or unauthorized") {
+            console.log('   ✓ 权限控制生效: 用户B无法更新用户A的笔记\n');
+        } else {
+            console.log('   ✗ 权限控制失效: 用户B竟然可以更新用户A的笔记!\n');
+            process.exit(1);
+        }
+
+        // 5. 验证用户B不能删除用户A的笔记
+        console.log('5. 测试权限控制: 用户B尝试删除用户A的笔记');
+        const deleteByBResponse = await deleteNote(userBToken, noteId);
+        console.log(`   状态码: ${deleteByBResponse.statusCode}`);
+        console.log(`   返回消息: ${deleteByBResponse.body?.message}`);
+        
+        if (deleteByBResponse.statusCode === 404 && 
+            deleteByBResponse.body?.message === "Note not found or unauthorized") {
+            console.log('   ✓ 权限控制生效: 用户B无法删除用户A的笔记\n');
+        } else {
+            console.log('   ✗ 权限控制失效: 用户B竟然可以删除用户A的笔记!\n');
+            process.exit(1);
+        }
+
+        // 6. 验证用户A可以更新自己的笔记
+        console.log('6. 验证正常功能: 用户A更新自己的笔记');
+        const updateByAResponse = await updateNote(userAToken, noteId, '用户A更新后的标题', '用户A更新后的内容');
+        console.log(`   状态码: ${updateByAResponse.statusCode}`);
+        console.log(`   更新后的标题: ${updateByAResponse.body?.title}`);
+        
+        if (updateByAResponse.statusCode === 200 && 
+            updateByAResponse.body?.title === '用户A更新后的标题') {
+            console.log('   ✓ 用户A可以正常更新自己的笔记\n');
+        } else {
+            console.log('   ✗ 用户A无法更新自己的笔记，这是不正常的\n');
+            process.exit(1);
+        }
+
+        // 7. 验证用户A可以删除自己的笔记
+        console.log('7. 验证正常功能: 用户A删除自己的笔记');
+        const deleteByAResponse = await deleteNote(userAToken, noteId);
+        console.log(`   状态码: ${deleteByAResponse.statusCode}`);
+        
+        if (deleteByAResponse.statusCode === 202) {
+            console.log('   ✓ 用户A可以正常删除自己的笔记\n');
+        } else {
+            console.log('   ✗ 用户A无法删除自己的笔记，这是不正常的\n');
+            process.exit(1);
+        }
+
+        console.log('========================================');
+        console.log('  所有测试通过! ✓');
+        console.log('========================================');
+        console.log('\n结论:');
+        console.log('- 用户A的笔记受到保护，用户B无法更新或删除');
+        console.log('- 权限控制使用了原子操作 (findOneAndUpdate / findOneAndDelete)');
+        console.log('- 这确保了权限检查和数据操作在同一个数据库操作中完成');
+        console.log('- 避免了竞态条件和权限绕过的风险');
+
+    } catch (error) {
+        console.error('\n测试执行出错:', error.message);
+        console.log('\n提示: 请确保:');
+        console.log('1. MongoDB 正在运行');
+        console.log('2. 服务器已启动 (运行 npm start)');
+        console.log('3. .env 文件已配置 MONGO_URL 和 SECRET_KEY');
+        process.exit(1);
+    }
+}
+
+runTests();