python: Let chilldkg have its own DKGOutput

README.md

@@ -648,6 +648,23 @@ public key.
 - `ThresholdError` - If `1 <= t <= len(hostpubkeys)` does not hold.
 - `OverflowError` - If `t >= 2^32` (so `t` cannot be serialized in 4 bytes).
 
+#### DKGOutput Tuples
+
+```python
+class DKGOutput(NamedTuple):
+secshare: Optional[bytes]
+threshold_pubkey: bytes
+pubshares: List[bytes]
+```
+
+Holds the outputs of a DKG session.
+
+*Attributes*:
+
+- `secshare` - Secret share of the participant (or `None` for coordinator)
+- `threshold_pubkey` - Senerated threshold public key representing the group
+- `pubshares` - Public shares of the participants
+
 #### participant\_step1
 
 ```python

python/chilldkg_ref/chilldkg.py

@@ -14,7 +14,6 @@
 from secp256k1ref.util import int_from_bytes, bytes_from_int
 
 from .vss import VSS, VSSCommitment
-from .simplpedpop import DKGOutput
 from . import encpedpop
 from .util import (
     BIP_TAG,
@@ -271,6 +270,22 @@ def params_id(params: SessionParams) -> bytes:
     return params_id
 
 
+# This is really the same definition as in simplpedpop and encpedpop. We repeat
+# it here only to have its docstring in this module.
+class DKGOutput(NamedTuple):
+    """Holds the outputs of a DKG session.
+
+    Attributes:
+        secshare: Secret share of the participant (or `None` for coordinator)
+        threshold_pubkey: Senerated threshold public key representing the group
+        pubshares: Public shares of the participants
+    """
+
+    secshare: Optional[bytes]
+    threshold_pubkey: bytes
+    pubshares: List[bytes]
+
+
 RecoveryData = NewType("RecoveryData", bytes)
 
 
@@ -429,12 +444,13 @@ def participant_step2(
     (params, idx, enc_state) = state1
     enc_cmsg, enc_secshares = cmsg1
 
-    dkg_output, eq_input = encpedpop.participant_step2(
+    enc_dkg_output, eq_input = encpedpop.participant_step2(
         enc_state, hostseckey, enc_cmsg, enc_secshares[idx]
     )
     # Include the enc_shares in eq_input to ensure that participants agree on all
     # shares, which in turn ensures that they have the right recovery data.
     eq_input += b"".join([bytes_from_int(int(share)) for share in enc_secshares])
+    dkg_output = DKGOutput._make(enc_dkg_output)  # Convert to chilldkg.DKGOutput type
     state2 = ParticipantState2(params, eq_input, dkg_output)
     sig = certeq_participant_step(hostseckey, idx, eq_input)
     pmsg2 = ParticipantMsg2(sig)
@@ -520,10 +536,11 @@ def coordinator_step1(
     params_validate(params)
     (hostpubkeys, t) = params
 
-    enc_cmsg, dkg_output, eq_input, enc_secshares = encpedpop.coordinator_step(
+    enc_cmsg, enc_dkg_output, eq_input, enc_secshares = encpedpop.coordinator_step(
         [pmsg1.enc_pmsg for pmsg1 in pmsgs1], t, hostpubkeys
     )
     eq_input += b"".join([bytes_from_int(int(share)) for share in enc_secshares])
+    dkg_output = DKGOutput._make(enc_dkg_output)  # Convert to chilldkg.DKGOutput type
     state = CoordinatorState(params, eq_input, dkg_output)
     cmsg1 = CoordinatorMsg1(enc_cmsg, enc_secshares)
     return state, cmsg1

python/tests.py

@@ -85,7 +85,7 @@ def simulate_encpedpop(seeds, t) -> List[Tuple[simplpedpop.DKGOutput, bytes]]:
 
 def simulate_chilldkg(
     seeds, t
-) -> List[Tuple[simplpedpop.DKGOutput, chilldkg.RecoveryData]]:
+) -> List[Tuple[chilldkg.DKGOutput, chilldkg.RecoveryData]]:
     n = len(seeds)
 
     hostpubkeys = []