diff --git a/minode/shared.py b/minode/shared.py
index d49786c..8c6a7d6 100644
--- a/minode/shared.py
+++ b/minode/shared.py
@@ -16,6 +16,8 @@ ip_enabled = True
 
 log_level = logging.INFO
 
+curve = 714  # secp256k1
+key_length = 32
 magic_bytes = b'\xe9\xbe\xb4\xd9'
 protocol_version = 3
 services = 3  # NODE_NETWORK, NODE_SSL
diff --git a/minode/structure.py b/minode/structure.py
index d2352fa..88ee6bc 100644
--- a/minode/structure.py
+++ b/minode/structure.py
@@ -132,6 +132,31 @@ class Object():
             return False
         return True
 
+    def is_junk(self):
+        """
+        Returns True if an object with encrypted payload has
+        curve number or key length different from those defined in shared.
+        """
+        if self.object_type not in (1, 2, 3):
+            return False
+        if self.object_type == 2:
+            sp = 0
+        elif self.object_type == 1 and self.version != 4:
+            return False
+        else:
+            sp = 32
+        sp += 16
+        curve = struct.unpack('!H', self.object_payload[sp:sp + 2])[0]
+        if curve != shared.curve:
+            return True
+        length = struct.unpack('!H', self.object_payload[sp + 2:sp + 4])[0]
+        if length > shared.key_length:
+            return True
+        length = struct.unpack('!H', self.object_payload[sp + 36:sp + 38])[0]
+        if length > shared.key_length:
+            return True
+        return False
+
     def pow_target(self):
         """Compute PoW target"""
         data = self.to_bytes()[8:]