diff --git a/owrx/controllers/__init__.py b/owrx/controllers/__init__.py
index 6839741..c00eebd 100644
--- a/owrx/controllers/__init__.py
+++ b/owrx/controllers/__init__.py
@@ -18,11 +18,7 @@ class Controller(object):
         if max_age is not None:
             headers["Cache-Control"] = "max-age: {0}".format(max_age)
         for key, value in headers.items():
-            if isinstance(value, list):
-                for v in value:
-                    self.handler.send_header(key, v)
-            else:
-                self.handler.send_header(key, value)
+            self.handler.send_header(key, value)
         self.handler.end_headers()
         if type(content) == str:
             content = content.encode()
diff --git a/owrx/controllers/receiverid.py b/owrx/controllers/receiverid.py
index 6489340..667c6be 100644
--- a/owrx/controllers/receiverid.py
+++ b/owrx/controllers/receiverid.py
@@ -6,16 +6,17 @@ from datetime import datetime
 class ReceiverIdController(Controller):
     def __init__(self, handler, request, options):
         super().__init__(handler, request, options)
-        self.authHeaders = []
+        self.authHeader = None
 
     def send_response(self, content, code=200, content_type="text/html", last_modified: datetime = None, max_age=None, headers=None):
-        if headers is None:
-            headers = {}
-        headers['Authorization'] = self.authHeaders
+        if self.authHeader is not None:
+            if headers is None:
+                headers = {}
+            headers['Authorization'] = self.authHeader
         super().send_response(content, code=code, content_type=content_type, last_modified=last_modified, max_age=max_age, headers=headers)
         pass
 
     def handle_request(self):
-        headers = self.request.headers.get_all("Authorization", [])
-        self.authHeaders = [ReceiverId.getResponseHeader(h) for h in headers]
+        if "Authorization" in self.request.headers:
+            self.authHeader = ReceiverId.getResponseHeader(self.request.headers['Authorization'])
         super().handle_request()
diff --git a/owrx/receiverid.py b/owrx/receiverid.py
index 33c62f0..847bb34 100644
--- a/owrx/receiverid.py
+++ b/owrx/receiverid.py
@@ -2,7 +2,7 @@ import re
 import logging
 import hashlib
 import hmac
-from datetime import datetime
+from datetime import datetime, timezone
 from owrx.config import Config
 
 logger = logging.getLogger(__name__)
@@ -38,18 +38,18 @@ class KeyChallenge(object):
 
 
 class KeyResponse(object):
-    def __init__(self, source, id, time: datetime, signature):
+    def __init__(self, source, id, time, signature):
         self.source = source
         self.id = id
         self.time = time
         self.signature = signature
 
     def __str__(self):
-        return "Time={time}, Response={source}-{id}-{signature}".format(
+        return "{source}-{id}-{time}-{signature}".format(
             source=self.source,
             id=self.id,
+            time=self.time,
             signature=self.signature,
-            time=self.time
         )
 
 
@@ -59,11 +59,16 @@ class ReceiverId(object):
         matches = headerRegex.match(requestHeader)
         if not matches:
             raise KeyException("invalid authorization header")
-        challenge = KeyChallenge(matches.group(1))
-        key = ReceiverId.findKey(challenge)
-        if key is None:
-            return {}
-        return ReceiverId.signChallenge(challenge, key)
+        challenges = [KeyChallenge(i) for i in matches.group(1).split(",")]
+
+        def signChallenge(challenge):
+            key = ReceiverId.findKey(challenge)
+            if key is None:
+                return
+            return ReceiverId.signChallenge(challenge, key)
+
+        responses = [signChallenge(c) for c in challenges]
+        return ",".join(str(r) for r in responses if r is not None)
 
     @staticmethod
     def findKey(challenge):
@@ -81,8 +86,9 @@ class ReceiverId(object):
 
     @staticmethod
     def signChallenge(challenge, key):
-        now = datetime.utcnow().isoformat()
+        now = datetime.utcnow().replace(microsecond=0, tzinfo=timezone.utc)
+        now_bytes = int(now.timestamp()).to_bytes(4, byteorder="big")
         m = hmac.new(bytes.fromhex(key.secret), digestmod=hashlib.sha256)
         m.update(bytes.fromhex(challenge.challenge))
-        m.update(now.encode('utf8'))
-        return KeyResponse(challenge.source, challenge.id, now, m.hexdigest())
+        m.update(now_bytes)
+        return KeyResponse(challenge.source, challenge.id, now_bytes.hex(), m.hexdigest())