feat: update witness serialization

waku/waku_rln_relay/conversion_utils.nim

@@ -117,17 +117,17 @@ proc serialize*(memIndices: seq[MembershipIndex]): seq[byte] =
   return memIndicesBytes
 
 proc serialize*(witness: Witness): seq[byte] =
-  ## Serializes the witness into a byte array
+  ## Serializes the witness into a byte array according to the RLN protocol format
   var buffer: seq[byte]
   buffer.add(witness.identity_secret)
-  buffer.add(witness.identity_nullifier)
-  for element in witness.merkle_proof:
-    buffer.add(element.toBytesBE()) # Convert Uint256 to big-endian bytes
+  buffer.add(witness.user_message_limit.toBytesBE())
+  buffer.add(witness.message_id.toBytesBE())
+  buffer.add(toBytes(uint64(witness.path_elements.len), Endianness.littleEndian))
+  for element in witness.path_elements:
+    buffer.add(element)
+  buffer.add(witness.identity_path_index)
+  buffer.add(witness.x)
   buffer.add(witness.external_nullifier)
-  buffer.add(uint8(witness.signal.len)) # Add signal length as a single byte
-  buffer.add(witness.signal)
-  buffer.add(toBytesBE(witness.message_id))
-  buffer.add(witness.rln_identifier)
   return buffer
 
 proc toEpoch*(t: uint64): Epoch =

waku/waku_rln_relay/group_manager/on_chain_sync/group_manager.nim

@@ -40,18 +40,17 @@ method generateProof*(
   if g.userMessageLimit.isNone():
     return err("user message limit is not set")
 
-  let merkleProof = g.fetchMerkleProof()
-
   # Prepare the witness
   let witness = Witness(
     identity_secret: g.idCredentials.get().idSecretHash,
-    identity_nullifier: g.idCredentials.get().idNullifier,
-    merkle_proof: merkleProof,
-    external_nullifier: epoch,
-    signal: data,
+    user_message_limit: g.userMessageLimit.get(),
     message_id: messageId,
-    rln_identifier: rlnIdentifier,
+    path_elements: g.fetchMerkleProof(),
+    identity_path_index: g.membershipIndex.get(),
+    x: data,
+    external_nullifier: poseidon_hash([epoch, rln_identifier]),
   )
+  
   let serializedWitness = serialize(witness)
   var inputBuffer = toBuffer(serializedWitness)
 

waku/waku_rln_relay/protocol_types.nim

@@ -54,12 +54,12 @@ type RateLimitProof* = object
 
 type Witness* = object ## Represents the custom witness for generating an RLN proof
   identity_secret*: seq[byte] # Identity secret (private key)
-  identity_nullifier*: seq[byte] # Identity nullifier
-  merkle_proof*: seq[Uint256] # Merkle proof elements (retrieved from the smart contract)
-  external_nullifier*: Epoch # Epoch (external nullifier)
-  signal*: seq[byte] # Message data (signal)
+  user_message_limit*: UserMessageLimit # Maximum number of messages a user can send
   message_id*: MessageId # Message ID (used for rate limiting)
-  rln_identifier*: RlnIdentifier # RLN identifier (default value provided)
+  path_elements*: seq[seq[byte]] # Merkle proof path elements
+  identity_path_index*: seq[byte] # Merkle proof path indices
+  x*: seq[byte] # Hash of the signal data
+  external_nullifier*: seq[byte] # Hash of epoch and RLN identifier
 
 type ProofMetadata* = object
   nullifier*: Nullifier