['''How can progress be guaranteed in a backwards-compatible way?''' In order to guarantee progress, it must be ensured that no deadlock occurs, i.e., no state is reached in which each party waits for the other party indefinitely. For example, any upgrade that adheres to the following conditions will guarantee progress:
-* The initiator must start by sending at least as many bytes as necessary to mismatch the magic/version 12 bytes prefix.
-* The responder must start sending after having received at least one byte that mismatches that 12-byte prefix.
+* The initiator must start by sending at least as many bytes as necessary to mismatch the magic/version 16 bytes prefix.
+* The responder must start sending after having received at least one byte that mismatches that 16-byte prefix.
* As soon as either party has received the other peer's garbage terminator, or has received 4095 bytes of garbage, they must send their own garbage terminator. (When either of these conditions is met, the other party has nothing to respond with anymore that would be needed to guarantee progress otherwise.)
* Whenever either party receives any nonzero number of bytes, while not having sent their garbage terminator completely yet, they must send at least one byte in response without waiting for more bytes.
* After either party has sent their garbage terminator, they must also send the garbage authentication packet without waiting for more bytes, and transition to the version negotiation phase.
@@ -338,16 +338,16 @@ def initiate_v2_handshake(peer, garbage_len):
send(peer, peer.ellswift_ours + peer.sent_garbage)
-The responder generates an ephemeral keypair for itself and derives the shared ECDH secret (using the first 64 received bytes) which enables it to instantiate the encrypted transport. It then sends 64 bytes of the unencrypted ElligatorSwift encoding of its own public key and its own ]responder_garbage
also of length garbage_len < 4096
. If the first 12 bytes received match the v1 prefix, the v1 protocol is used instead.
+The responder generates an ephemeral keypair for itself and derives the shared ECDH secret (using the first 64 received bytes) which enables it to instantiate the encrypted transport. It then sends 64 bytes of the unencrypted ElligatorSwift encoding of its own public key and its own responder_garbage
also of length garbage_len < 4096
. If the first 16 bytes received match the v1 prefix, the v1 protocol is used instead.
TRANSPORT_VERSION = b''
NETWORK_MAGIC = b'\xf9\xbe\xb4\xd9' # Mainnet network magic; differs on other networks.
-V1_PREFIX = NETWORK_MAGIC + b'version\x00'
+V1_PREFIX = NETWORK_MAGIC + b'version\x00\x00\x00\x00\x00'
def respond_v2_handshake(peer, garbage_len):
peer.received_prefix = b""
- while len(peer.received_prefix) < 12:
+ while len(peer.received_prefix) < len(V1_PREFIX):
peer.received_prefix += receive(peer, 1)
if peer.received_prefix[-1] != V1_PREFIX[len(peer.received_prefix) - 1]:
peer.privkey_ours, peer.ellswift_ours = ellswift_create()