diff --git a/backend/IM_API/Dtos/BaseResponse.cs b/backend/IM_API/Dtos/BaseResponse.cs
new file mode 100644
index 0000000..e238946
--- /dev/null
+++ b/backend/IM_API/Dtos/BaseResponse.cs
@@ -0,0 +1,57 @@
+namespace IM_API.Dtos
+{
+    public class BaseResponse<T>
+    {
+        //响应状态码
+        public int Code { get; set; }
+        //响应消息
+        public string Message { get; set; }
+        //响应数据
+        public T? Data { get; set; }
+        /// <summary>
+        /// 默认成功响应返回
+        /// </summary>
+        /// <param name="msg"></param>
+        /// <param name="data"></param>
+        public BaseResponse(string msg,T data)
+        {
+            this.Code = 0;
+            this.Message = msg;
+            this.Data = data;
+        }
+        /// <summary>
+        /// 默认成功响应返回，不带数据
+        /// </summary>
+        /// <param name="msg"></param>
+        /// <param name="data"></param>
+        public BaseResponse(string msg)
+        {
+            this.Code = 0;
+            this.Message = msg;
+        }
+        /// <summary>
+        /// 非成功响应且带数据
+        /// </summary>
+        /// <param name="code"></param>
+        /// <param name="message"></param>
+        /// <param name="data"></param>
+        public BaseResponse(int code, string message, T? data)
+        {
+            Code = code;
+            Message = message;
+            Data = data;
+        }
+        /// <summary>
+        /// 非成功响应且不带数据
+        /// </summary>
+        /// <param name="code"></param>
+        /// <param name="message"></param>
+        /// <param name="data"></param>
+        public BaseResponse(int code, string message)
+        {
+            Code = code;
+            Message = message;
+        }
+        public BaseResponse() { }
+    }
+}
diff --git a/backend/IM_API/Dtos/FriendRequestDto.cs b/backend/IM_API/Dtos/FriendRequestDto.cs
new file mode 100644
index 0000000..8990d96
--- /dev/null
+++ b/backend/IM_API/Dtos/FriendRequestDto.cs
@@ -0,0 +1,9 @@
+namespace IM_API.Dtos
+{
+    public class FriendRequestDto
+    {
+        public int FromUserId { get; set; }
+        public int ToUserId { get; set; }
+        public string? Description { get; set; }
+    }
+}
diff --git a/backend/IM_API/Dtos/LoginDto.cs b/backend/IM_API/Dtos/LoginDto.cs
new file mode 100644
index 0000000..03cd5e0
--- /dev/null
+++ b/backend/IM_API/Dtos/LoginDto.cs
@@ -0,0 +1,9 @@
+namespace IM_API.Dtos
+{
+    public class LoginDto
+    {
+        public int Id { get; set; }
+        public string Token { get; set; }
+        public string RefreshToken { get; set; }
+    }
+}
diff --git a/backend/IM_API/Dtos/LoginRequestDto.cs b/backend/IM_API/Dtos/LoginRequestDto.cs
new file mode 100644
index 0000000..b1c1b1f
--- /dev/null
+++ b/backend/IM_API/Dtos/LoginRequestDto.cs
@@ -0,0 +1,8 @@
+namespace IM_API.Dtos
+{
+    public class LoginRequestDto
+    {
+        public string Username { get; set; }
+        public string Password { get; set; }
+    }
+}
diff --git a/backend/IM_API/Dtos/RegisterRequestDto.cs b/backend/IM_API/Dtos/RegisterRequestDto.cs
new file mode 100644
index 0000000..e4ac4d0
--- /dev/null
+++ b/backend/IM_API/Dtos/RegisterRequestDto.cs
@@ -0,0 +1,8 @@
+namespace IM_API.Dtos
+{
+    public class RegisterRequestDto
+    {
+        public string Username { get; set; }
+        public string Password { get; set; }
+    }
+}
diff --git a/backend/IM_API/Dtos/UpdateUserDto.cs b/backend/IM_API/Dtos/UpdateUserDto.cs
new file mode 100644
index 0000000..279018d
--- /dev/null
+++ b/backend/IM_API/Dtos/UpdateUserDto.cs
@@ -0,0 +1,7 @@
+namespace IM_API.Dtos
+{
+    public class UpdateUserDto
+    {
+        public string? NickName { get; set; }
+    }
+}
diff --git a/backend/IM_API/Dtos/UserInfoDto.cs b/backend/IM_API/Dtos/UserInfoDto.cs
new file mode 100644
index 0000000..fff482a
--- /dev/null
+++ b/backend/IM_API/Dtos/UserInfoDto.cs
@@ -0,0 +1,38 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace IM_API.Dtos
+{
+    public class UserInfoDto
+    {
+        public int Id { get; set; }
+
+        /// <summary>
+        /// 唯一用户名
+        /// </summary>
+        public string Username { get; set; }
+
+        /// <summary>
+        /// 用户昵称
+        /// </summary>
+        public string NickName { get; set; }
+
+        /// <summary>
+        /// 用户在线状态
+        /// 0（默认）：不在线
+        /// 1：在线
+        /// </summary>
+        public sbyte OlineStatus { get; set; }
+
+        /// <summary>
+        /// 创建时间
+        /// </summary>
+        public DateTime Created { get; set; }
+
+        /// <summary>
+        /// 账户状态
+        /// (0：未激活,1：正常,2：封禁)
+        /// </summary>
+        public sbyte Status { get; set; }
+    }
+}
diff --git a/backend/IM_API/IM_API.csproj b/backend/IM_API/IM_API.csproj
index 4610176..1f6fe1f 100644
--- a/backend/IM_API/IM_API.csproj
+++ b/backend/IM_API/IM_API.csproj
@@ -21,6 +21,7 @@
     <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.22.1" />
     <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="8.0.3" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
+    <PackageReference Include="System.IdentityModel.Tokens.Jwt" Version="8.14.0" />
   </ItemGroup>
 
 </Project>
diff --git a/backend/IM_API/Interface/Services/IAuthService.cs b/backend/IM_API/Interface/Services/IAuthService.cs
index 770cceb..38b493f 100644
--- a/backend/IM_API/Interface/Services/IAuthService.cs
+++ b/backend/IM_API/Interface/Services/IAuthService.cs
@@ -1,6 +1,39 @@
-namespace IM_API.Interface.Services
+using IM_API.Dtos;
+using IM_API.Models;
+
+namespace IM_API.Interface.Services
 {
     public interface IAuthService
     {
+        /// <summary>
+        /// 登录
+        /// </summary>
+        /// <param name="dto"></param>
+        /// <returns></returns>
+        Task<LoginDto> LoginAsync(LoginRequestDto dto);
+        /// <summary>
+        /// 注册
+        /// </summary>
+        /// <param name="dto"></param>
+        /// <returns></returns>
+        Task<UserInfoDto> RegisterAsync(RegisterRequestDto dto);
+        /// <summary>
+        /// 生成登录凭证
+        /// </summary>
+        /// <param name="user"></param>
+        /// <returns></returns>
+        string GenerateToken(User user);
+        /// <summary>
+        /// 验证登录凭证
+        /// </summary>
+        /// <param name="token"></param>
+        /// <returns></returns>
+        int? ValidateToken(string token);
+        /// <summary>
+        /// 刷新令牌
+        /// </summary>
+        /// <param name="refreshToken"></param>
+        /// <returns></returns>
+        LoginDto RefreshToken(string refreshToken);
     }
 }
diff --git a/backend/IM_API/Interface/Services/IFriendSerivce.cs b/backend/IM_API/Interface/Services/IFriendSerivce.cs
new file mode 100644
index 0000000..ecd620d
--- /dev/null
+++ b/backend/IM_API/Interface/Services/IFriendSerivce.cs
@@ -0,0 +1,32 @@
+using IM_API.Dtos;
+using IM_API.Models;
+
+namespace IM_API.Interface.Services
+{
+    public interface IFriendSerivce
+    {
+        /// <summary>
+        /// 获取好友列表
+        /// </summary>
+        /// <param name="userId">指定用户</param>
+        /// <param name="page">当前页</param>
+        /// <param name="limit">分页大小</param>
+        /// <returns></returns>
+        Task<List<UserInfoDto>> GetFriendListAsync(int userId,int page,int limit);
+        /// <summary>
+        /// 新增好友请求
+        /// </summary>
+        /// <param name="friendRequest"></param>
+        /// <returns></returns>
+        Task<bool> SendFriendRequestAsync(FriendRequestDto friendRequest);
+        /// <summary>
+        /// 获取好友请求
+        /// </summary>
+        /// <param name="userId"></param>
+        /// <param name="isReceived">是否为接受请求方</param>
+        /// <param name="page"></param>
+        /// <param name="limit"></param>
+        /// <returns></returns>
+        Task<Friendrequest> GetFriendRequestListAsync(int userId,bool isReceived,int page,int limit);
+    }
+}
diff --git a/backend/IM_API/Interface/Services/IUserService.cs b/backend/IM_API/Interface/Services/IUserService.cs
new file mode 100644
index 0000000..b11f2c3
--- /dev/null
+++ b/backend/IM_API/Interface/Services/IUserService.cs
@@ -0,0 +1,39 @@
+using IM_API.Dtos;
+using IM_API.Models;
+
+namespace IM_API.Interface.Services
+{
+    public interface IUserService
+    {
+        /// <summary>
+        /// 获取用户信息
+        /// </summary>
+        /// <param name="userId"></param>
+        /// <returns></returns>
+        Task<UserInfoDto> GetUserInfoAsync(int userId);
+        /// <summary>
+        /// 用户名查找用户
+        /// </summary>
+        /// <param name="username"></param>
+        /// <returns></returns>
+        Task<UserInfoDto> GetUserInfoByUsernameAsync(string username);
+        /// <summary>
+        /// 更新用户信息
+        /// </summary>
+        /// <param name="dto"></param>
+        /// <returns></returns>
+        Task<UserInfoDto> UpdateUserAsync(UpdateUserDto dto);
+        /// <summary>
+        /// 重置用户密码
+        /// </summary>
+        /// <param name="password"></param>
+        /// <returns></returns>
+        Task<bool> ResetPasswordAsync(string password);
+        /// <summary>
+        /// 更新用户在线状态
+        /// </summary>
+        /// <param name="onlineStatus"></param>
+        /// <returns></returns>
+        Task<bool> UpdateOlineStatusAsync(UserOnlineStatus onlineStatus);
+    }
+}
diff --git a/backend/IM_API/Models/FriendStatus.cs b/backend/IM_API/Models/FriendStatus.cs
new file mode 100644
index 0000000..08324a8
--- /dev/null
+++ b/backend/IM_API/Models/FriendStatus.cs
@@ -0,0 +1,7 @@
+namespace IM_API.Models
+{
+    public enum FriendStatus:SByte
+    {
+
+    }
+}
diff --git a/backend/IM_API/Models/User.cs b/backend/IM_API/Models/User.cs
index 55bcdb3..b1639a3 100644
--- a/backend/IM_API/Models/User.cs
+++ b/backend/IM_API/Models/User.cs
@@ -41,7 +41,7 @@ public partial class User
     /// 1：在线
     /// </summary>
     [Column(TypeName = "tinyint(4)")]
-    public sbyte OlineStatus { get; set; }
+    public UserOnlineStatus OlineStatus { get; set; }
 
     /// <summary>
     /// 创建时间
@@ -60,7 +60,7 @@ public partial class User
     /// (0：未激活,1：正常,2：封禁)
     /// </summary>
     [Column(TypeName = "tinyint(4)")]
-    public sbyte Status { get; set; }
+    public UserStatus Status { get; set; }
 
     /// <summary>
     /// 软删除标识
diff --git a/backend/IM_API/Models/UserOlineStatus.cs b/backend/IM_API/Models/UserOlineStatus.cs
new file mode 100644
index 0000000..ac3f15f
--- /dev/null
+++ b/backend/IM_API/Models/UserOlineStatus.cs
@@ -0,0 +1,18 @@
+namespace IM_API.Models
+{
+    /// <summary>
+    /// 用户在线状态
+    /// </summary>
+    public enum UserOnlineStatus : sbyte
+    {
+        /// <summary>
+        /// 不在线 (0)
+        /// </summary>
+        Offline = 0,
+
+        /// <summary>
+        /// 在线 (1)
+        /// </summary>
+        Online = 1
+    }
+}
diff --git a/backend/IM_API/Models/UserStatus.cs b/backend/IM_API/Models/UserStatus.cs
new file mode 100644
index 0000000..e08f38b
--- /dev/null
+++ b/backend/IM_API/Models/UserStatus.cs
@@ -0,0 +1,9 @@
+namespace IM_API.Models
+{
+    public enum UserStatus:SByte
+    {
+        Inactive = 0,
+        Normal = 1,
+        Banned = 2
+    }
+}
diff --git a/backend/IM_API/Tools/PasswordHasher.cs b/backend/IM_API/Tools/PasswordHasher.cs
new file mode 100644
index 0000000..b567cc4
--- /dev/null
+++ b/backend/IM_API/Tools/PasswordHasher.cs
@@ -0,0 +1,22 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace IM_API.Tools
+{
+    public static class PasswordHasher
+    {
+        public static string HashPassword(string password)
+        {
+            using var sha256 = SHA256.Create();
+            var hashedBytes = sha256.ComputeHash(Encoding.UTF8.GetBytes(password));
+            return Convert.ToBase64String(hashedBytes);
+        }
+
+        public static bool VerifyPassword(string password, string hashedPassword)
+        {
+            var hashedInput = HashPassword(password);
+            return hashedInput == hashedPassword;
+        }
+    }
+}
+}