diff --git a/libraries/ArduinoOTA/ArduinoOTA.cpp b/libraries/ArduinoOTA/ArduinoOTA.cpp
index e9e0a3464..fd24bf100 100644
--- a/libraries/ArduinoOTA/ArduinoOTA.cpp
+++ b/libraries/ArduinoOTA/ArduinoOTA.cpp
@@ -6,6 +6,8 @@
 
 //#define OTA_DEBUG 1
 
+#define U_AUTH 200
+
 ArduinoOTAClass::ArduinoOTAClass()
 {
     _udp_ota = new WiFiUDP();
@@ -169,12 +171,17 @@ void ArduinoOTAClass::handle() {
   if (!_udp_ota->parsePacket()) return;
 
   if(_state == OTA_IDLE){
+    int cmd = _udp_ota->parseInt();
+    if(cmd != U_FLASH && cmd != U_SPIFFS)
+      return;
     _ota_ip = _udp_ota->remoteIP();
-    _cmd  = _udp_ota->parseInt();
+    _cmd  = cmd;
     _ota_port = _udp_ota->parseInt();
     _size = _udp_ota->parseInt();
     _udp_ota->read();
     sprintf(_md5, "%s", _udp_ota->readStringUntil('\n').c_str());
+    if(strlen(_md5) != 32)
+      return;
 
 #if OTA_DEBUG
     Serial.print("Update Start: ip:");
@@ -199,8 +206,18 @@ void ArduinoOTAClass::handle() {
       _state = OTA_RUNUPDATE;
     }
   } else if(_state == OTA_WAITAUTH){
+    int cmd = _udp_ota->parseInt();
+    if(cmd != U_AUTH){
+      _state = OTA_IDLE;
+      return;
+    }
+    _udp_ota->read();
     String cnonce = _udp_ota->readStringUntil(' ');
     String response = _udp_ota->readStringUntil('\n');
+    if(cnonce.length() != 32 || response.length() != 32){
+      _state = OTA_IDLE;
+      return;
+    }
     
     MD5Builder _passmd5;
     _passmd5.begin();
diff --git a/tools/espota.py b/tools/espota.py
index a07c8d61c..c03e1c4a7 100755
--- a/tools/espota.py
+++ b/tools/espota.py
@@ -34,6 +34,7 @@ import hashlib
 # Commands
 FLASH = 0
 SPIFFS = 100
+AUTH = 200
 
 
 def serve(remoteAddr, remotePort, password, filename, command = FLASH):
@@ -78,7 +79,7 @@ def serve(remoteAddr, remotePort, password, filename, command = FLASH):
       result = hashlib.md5(result_text).hexdigest()
       sys.stderr.write('Authenticating...')
       sys.stderr.flush()
-      message = '%s %s\n' % (cnonce, result)
+      message = '%d %s %s\n' % (AUTH, cnonce, result)
       sock2.sendto(message, remote_address)
       sock2.settimeout(10)
       try: