python: add license file and re-write to error msg

Author: siv2r

bip-frost-signing.md

@@ -6,8 +6,8 @@ Comments-URI:
 Status: Draft
 Type: Standards Track
 Assigned: ?
-License: CC0-1.0 or MIT
-Post-History: https://groups.google.com/g/bitcoindev/c/PeMp2HQl-H4/m/AcJtK0aKAwAJ
+License: CC0-1.0
+Discussion: 2024-07-31: https://groups.google.com/g/bitcoindev/c/PeMp2HQl-H4/m/AcJtK0aKAwAJ
 Requires: 32, 340, 341
 ```
 
@@ -783,6 +783,7 @@ This document proposes a standard for the FROST threshold signature scheme that
 
 ## Changelog
 
+- *0.3.6* (2026-01-28): Add MIT license file for reference code and other auxiliary files.
 - *0.3.5* (2026-01-25): Update secp256k1lab to latest version, remove stub file, and fix formatting in the BIP text.
 - *0.3.4* (2026-01-01): Add an example file to the reference code.
 - *0.3.3* (2025-12-29): Replace the lengthy Introduction section with a concise Motivation section.

bip-frost-signing/COPYING

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2024-2026 Sivaram Dhakshinamoorthy
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

bip-frost-signing/python/frost_ref/signing.py

@@ -47,6 +47,7 @@ def __init__(self, signer_id: Optional[int], contrib: ContribKind) -> None:
 def derive_interpolating_value(ids: List[int], my_id: int) -> Scalar:
     assert my_id in ids
     assert 0 <= my_id < 2**32
+    assert len(set(ids)) == len(ids)
     num = Scalar(1)
     deno = Scalar(1)
     for curr_id in ids:
@@ -95,9 +96,7 @@ def validate_signers_ctx(signers_ctx: SignersContext) -> None:
         except ValueError:
             raise InvalidContributionError(i, "pubshare")
     if len(set(ids)) != len(ids):
-        raise ValueError(
-            "The participant identifier list must contain unique elements."
-        )
+        raise ValueError("The participant identifier list contains duplicate elements.")
     if derive_thresh_pubkey(ids, pubshares) != thresh_pk:
         raise ValueError("The provided key material is incorrect.")
 

bip-frost-signing/python/vectors/det_sign_vectors.json

@@ -258,7 +258,7 @@
             "signer_index": 0,
             "error": {
                 "type": "ValueError",
-                "message": "The participant identifier list must contain unique elements."
+                "message": "The participant identifier list contains duplicate elements."
             },
             "comment": "The participant identifier list contains duplicate elements"
         },

bip-frost-signing/python/vectors/sign_verify_vectors.json

@@ -218,7 +218,7 @@
             "secnonce_index": 0,
             "error": {
                 "type": "ValueError",
-                "message": "The participant identifier list must contain unique elements."
+                "message": "The participant identifier list contains duplicate elements."
             },
             "comment": "The participant identifier list contains duplicate elements"
         },