SECURITY Include eq_input in signed message

sigh
BlockstreamResearch · Oct 23, 2024 · 1a2dd1b · 1a2dd1b
1 parent 8e052d9
commit 1a2dd1b
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/python/chilldkg_ref/chilldkg.py b/python/chilldkg_ref/chilldkg.py
@@ -83,7 +83,7 @@ class InvalidRecoveryDataError(Exception):
 
 
 def certeq_message(x: bytes, idx: int) -> bytes:
-    return idx.to_bytes(4, "big")
+    return idx.to_bytes(4, "big") + x
 
 
 def certeq_participant_step(hostseckey: bytes, idx: int, x: bytes) -> bytes:
@@ -634,7 +634,8 @@ def recover(
     params_validate(params)
 
     # Verify cert
-    certeq_verify(hostpubkeys, recovery_data[: 64 * n], cert)
+    eq_input = recovery_data[: -len(cert)]
+    certeq_verify(hostpubkeys, eq_input, cert)
 
     # Compute threshold pubkey and individual pubshares
     threshold_pubkey = sum_coms.commitment_to_secret()