1 files changed, 39 insertions, 0 deletions
diff --git a/packages/meshbay-common/src/meshbay_common/device.py b/packages/meshbay-common/src/meshbay_common/device.py
index 8951dbb..cfa8dd6 100644
--- a/packages/meshbay-common/src/meshbay_common/device.py
+++ b/packages/meshbay-common/src/meshbay_common/device.py
@@ -36,6 +36,7 @@ import hashlib
 
 DEVICE_REQUEST_PREFIX = b"meshbay:device_req:v1"
 DEVICE_ADD_PREFIX = b"meshbay:device_add:v1"
+DEVICE_HELLO_PREFIX = b"meshbay:device_hello:v1"
 
 # Same as the join and admin transcripts: interactive exchanges that complete in
 # milliseconds, so anything older is a replay.
@@ -123,3 +124,41 @@ def device_add_transcript(
         nonce_node,
         str(ts).encode(),
     ])
+
+
+def device_hello_transcript(
+    node_pk_b64: str,
+    group_id: str,
+    user_id: str,
+    pk_ed25519_b64: str,
+    nonce_node: bytes,
+    ts: int,
+) -> bytes:
+    """
+    Signed by the device on an already-authenticated connection, saying **which
+    of the account's devices this connection is**.
+
+    The handshake proves membership of a group (a GEK-HMAC) and carries an
+    account from the hub's token; it proves nothing about *which* device is
+    talking. The node needed that the moment one account could hold several:
+    `_load_pinned_pk` was resolving "this account's oldest live device" and
+    recording it as the uploader of every file, so a phone's uploads were
+    attributed to a laptop.
+
+    Additive and optional. A client that does not send it leaves the node where
+    it was, which is why this could ship without a breaking protocol change —
+    but a node that *has* been told refuses a later claim to be a different
+    device on the same connection.
+
+    `nonce_node` is this connection's handshake nonce, so the signature cannot
+    be lifted onto another connection, and `node_pk` binds it to one node —
+    the same rule as every other transcript here.
+    """
+    return _pack(DEVICE_HELLO_PREFIX, [
+        node_pk_b64.encode(),
+        group_id.encode(),
+        user_id.encode(),
+        pk_ed25519_b64.encode(),
+        nonce_node,
+        str(ts).encode(),
+    ])