tally

commit b5aff2ecb7500636473960b19110116ad7e0da48
parent 3a7c7f55b7b1f890f198418b9aff14cf03aaa15b
author Owen Rusk <owen@papermothgames.com>
date   2024-07-17 16:05:51 -0500

join: say so when the same share is given twice

it used to fall over with a traceback from combine.

diff --git a/tally/cli.py b/tally/cli.py
index a77bee1..f5a9c37 100644
--- a/tally/cli.py
+++ b/tally/cli.py
@@ -25,6 +25,11 @@ def cmd_join(args: argparse.Namespace) -> int:
     if len({s.id for s in shares}) > 1:
         raise ShareError("these shares come from different splits")
     k = shares[0].k
+    seen: dict[int, int] = {}
+    for i, s in enumerate(shares, 1):
+        if s.x in seen:
+            raise ShareError(f"shares {seen[s.x]} and {i} are both share {s.x} of the split")
+        seen[s.x] = i
     if len(shares) < k:
         raise ShareError(f"need {k} shares, got {len(shares)}")
     secret = shamir.combine([(s.x, s.data) for s in shares[:k]])