bip327: minor fixes

- An error test vector doesn’t specify the InvalidContributionError type
- In *DeterministicSign*, use GetXonlyPubkey instead of GetPubkey
- The key_agg_and_tweak fn doesn’t specify the return type
- In partial_sig_verify_internal, the pubkey arg should be PlainPk
- Remove unused enumerate() fn calls
- In test_sign_verify, add an additional assert statement

4 files changed, 19 insertions, 14 deletions

diff --git a/bip-0327.mediawiki b/bip-0327.mediawiki
index b659629..77a0024 100644
--- a/bip-0327.mediawiki
+++ b/bip-0327.mediawiki
@@ -619,7 +619,7 @@ Algorithm ''DeterministicSign(sk, aggothernonce, pk<sub>1..u</sub>, tweak<sub>1.
 * Let ''keyagg_ctx<sub>0</sub> = KeyAgg(pk<sub>1..u</sub>)''; fail if that fails
 * For ''i = 1 .. v'':
 ** Let ''keyagg_ctx<sub>i</sub> = ApplyTweak(keyagg_ctx<sub>i-1</sub>, tweak<sub>i</sub>, is_xonly_t<sub>i</sub>)''; fail if that fails
-* Let ''aggpk = GetPubkey(keyagg_ctx<sub>v</sub>)''
+* Let ''aggpk = GetXonlyPubkey(keyagg_ctx<sub>v</sub>)''
 * Let ''k<sub>i</sub> = int(hash<sub>MuSig/deterministic/nonce</sub>(sk' || aggothernonce || aggpk || bytes(8, len(m)) || m || bytes(1, i - 1))) mod n'' for ''i = 1,2''
 * Fail if ''k<sub>1</sub> = 0'' or ''k<sub>2</sub> = 0''
 * Let ''R<sub>⁎,1</sub> = k<sub>1</sub>⋅G, R<sub>⁎,2</sub> = k<sub>2</sub>⋅G''
diff --git a/bip-0327/gen_vectors_helper.py b/bip-0327/gen_vectors_helper.py
index a70bb6f..03c2dbb 100644
--- a/bip-0327/gen_vectors_helper.py
+++ b/bip-0327/gen_vectors_helper.py
@@ -153,7 +153,8 @@ def sig_agg_vectors():
         "psig_indices": [7, 8],
         "error": {
             "type": "invalid_contribution",
-            "signer": 1
+            "signer": 1,
+            "contrib": "psig",
         },
         "comment": "Partial signature is invalid because it exceeds group size"
     }
diff --git a/bip-0327/reference.py b/bip-0327/reference.py
index edf6e76..cc1af50 100644
--- a/bip-0327/reference.py
+++ b/bip-0327/reference.py
@@ -317,7 +317,7 @@ SessionContext = NamedTuple('SessionContext', [('aggnonce', bytes),
                                                ('is_xonly', List[bool]),
                                                ('msg', bytes)])
 
-def key_agg_and_tweak(pubkeys: List[PlainPk], tweaks: List[bytes], is_xonly: List[bool]):
+def key_agg_and_tweak(pubkeys: List[PlainPk], tweaks: List[bytes], is_xonly: List[bool]) -> KeyAggContext:
     if len(tweaks) != len(is_xonly):
         raise ValueError('The `tweaks` and `is_xonly` arrays must have the same length.')
     keyagg_ctx = key_agg(pubkeys)
@@ -367,7 +367,7 @@ def sign(secnonce: bytearray, sk: bytes, session_ctx: SessionContext) -> bytes:
         raise ValueError('secret key value is out of range.')
     P = point_mul(G, d_)
     assert P is not None
-    pk = cbytes(P)
+    pk = PlainPk(cbytes(P))
     if not pk == secnonce[64:97]:
         raise ValueError('Public key does not match nonce_gen argument')
     a = get_session_key_agg_coeff(session_ctx, P)
@@ -430,7 +430,7 @@ def partial_sig_verify(psig: bytes, pubnonces: List[bytes], pubkeys: List[PlainP
     session_ctx = SessionContext(aggnonce, pubkeys, tweaks, is_xonly, msg)
     return partial_sig_verify_internal(psig, pubnonces[i], pubkeys[i], session_ctx)
 
-def partial_sig_verify_internal(psig: bytes, pubnonce: bytes, pk: bytes, session_ctx: SessionContext) -> bool:
+def partial_sig_verify_internal(psig: bytes, pubnonce: bytes, pk: PlainPk, session_ctx: SessionContext) -> bool:
     (Q, gacc, _, b, R, e) = get_session_values(session_ctx)
     s = int_from_bytes(psig)
     if s >= n:
@@ -523,7 +523,7 @@ def test_key_agg_vectors() -> None:
 
         assert get_xonly_pk(key_agg(pubkeys)) == expected
 
-    for i, test_case in enumerate(error_test_cases):
+    for test_case in error_test_cases:
         exception, except_fn = get_error_details(test_case)
 
         pubkeys = [X[i] for i in test_case["key_indices"]]
@@ -572,7 +572,7 @@ def test_nonce_agg_vectors() -> None:
         expected = bytes.fromhex(test_case["expected"])
         assert nonce_agg(pubnonces) == expected
 
-    for i, test_case in enumerate(error_test_cases):
+    for test_case in error_test_cases:
         exception, except_fn = get_error_details(test_case)
         pubnonces = [pnonce[i] for i in test_case["pnonce_indices"]]
         assert_raises(exception, lambda: nonce_agg(pubnonces), except_fn)
@@ -598,7 +598,10 @@ def test_sign_verify_vectors() -> None:
 
     aggnonces = fromhex_all(test_data["aggnonces"])
     # The aggregate of the first three elements of pnonce is at index 0
-    assert(aggnonces[0] == nonce_agg([pnonce[0], pnonce[1], pnonce[2]]))
+    assert (aggnonces[0] == nonce_agg([pnonce[0], pnonce[1], pnonce[2]]))
+    # The aggregate of the first and fourth elements of pnonce is at index 1,
+    # which is the infinity point encoded as a zeroed 33-byte array
+    assert (aggnonces[1] == nonce_agg([pnonce[0], pnonce[3]]))
 
     msgs = fromhex_all(test_data["msgs"])
 
@@ -626,7 +629,7 @@ def test_sign_verify_vectors() -> None:
         assert sign(secnonce_tmp, sk, session_ctx) == expected
         assert partial_sig_verify(expected, pubnonces, pubkeys, [], [], msg, signer_index)
 
-    for i, test_case in enumerate(sign_error_test_cases):
+    for test_case in sign_error_test_cases:
         exception, except_fn = get_error_details(test_case)
 
         pubkeys = [X[i] for i in test_case["key_indices"]]
@@ -646,7 +649,7 @@ def test_sign_verify_vectors() -> None:
 
         assert not partial_sig_verify(sig, pubnonces, pubkeys, [], [], msg, signer_index)
 
-    for i, test_case in enumerate(verify_error_test_cases):
+    for test_case in verify_error_test_cases:
         exception, except_fn = get_error_details(test_case)
 
         sig = bytes.fromhex(test_case["sig"])
@@ -702,7 +705,7 @@ def test_tweak_vectors() -> None:
         assert sign(secnonce_tmp, sk, session_ctx) == expected
         assert partial_sig_verify(expected, pubnonces, pubkeys, tweaks, is_xonly, msg, signer_index)
 
-    for i, test_case in enumerate(error_test_cases):
+    for test_case in error_test_cases:
         exception, except_fn = get_error_details(test_case)
 
         pubkeys = [X[i] for i in test_case["key_indices"]]
@@ -747,7 +750,7 @@ def test_det_sign_vectors() -> None:
         session_ctx = SessionContext(aggnonce, pubkeys, tweaks, is_xonly, msg)
         assert partial_sig_verify_internal(psig, pubnonce, pubkeys[signer_index], session_ctx)
 
-    for i, test_case in enumerate(error_test_cases):
+    for test_case in error_test_cases:
         exception, except_fn = get_error_details(test_case)
 
         pubkeys = [X[i] for i in test_case["key_indices"]]
@@ -796,7 +799,7 @@ def test_sig_agg_vectors() -> None:
         aggpk = get_xonly_pk(key_agg_and_tweak(pubkeys, tweaks, is_xonly))
         assert schnorr_verify(msg, aggpk, sig)
 
-    for i, test_case in enumerate(error_test_cases):
+    for test_case in error_test_cases:
         exception, except_fn = get_error_details(test_case)
 
         pubnonces = [pnonce[i] for i in test_case["nonce_indices"]]
diff --git a/bip-0327/vectors/sig_agg_vectors.json b/bip-0327/vectors/sig_agg_vectors.json
index 04a7bc6..519562c 100644
--- a/bip-0327/vectors/sig_agg_vectors.json
+++ b/bip-0327/vectors/sig_agg_vectors.json
@@ -143,7 +143,8 @@
             ],
             "error": {
                 "type": "invalid_contribution",
-                "signer": 1
+                "signer": 1,
+                "contrib": "psig"
             },
             "comment": "Partial signature is invalid because it exceeds group size"
         }