fix: set gossip validation mode to StrictNoSign (Anonymous) (leanEthereum#72)

* fix: set gossip validation mode to StrictNoSign (Anonymous)

* fix: make linter happy

Author: unnawut

docs/client/networking.md

@@ -99,9 +99,11 @@ data being sent on the topic and how the data field of the message is encoded.
   bytes that will be transmitted over the wire. See the [Encodings](#Encodings)
   section for further details.
 
-The optional `from` (1), `seqno` (3), `signature` (5) and `key` (6) protobuf
+The `from` (1), `seqno` (3), `signature` (5) and `key` (6) protobuf
 fields are omitted from the message, since messages are identified by content,
-anonymous, and signed where necessary in the application layer.
+anonymous, and signed where necessary in the application layer. Clients MUST
+enforce this by applying the `StrictNoSign` signature policy (aka `Anonymous`
+in some implementations).
 
 The `message-id` MUST be the following 20 byte value computed from the message:
 

src/lean_spec/subspecs/networking/gossipsub.py

@@ -63,6 +63,13 @@ class GossipsubParameters(StrictBaseModel):
     This is calculated as SECONDS_PER_SLOT * JUSTIFICATION_LOOKBACK_SLOTS * 2.
     """
 
+    validation_mode: str = "strict_no_sign"
+    """The message validation mode. `strict_no_sign` requires the author,
+    sequence number and signature fields of a message to be empty. Any message
+    that contains these fields is considered invalid. In some libp2p
+    implementations, this mode is also known as Anonymous mode.
+    """
+
 
 MessageId = Annotated[bytes, Field(min_length=20, max_length=20)]
 """A 20-byte ID for gossipsub messages."""