move DKGIndexMap formal specs up

model/flow/dkg.go

@@ -37,9 +37,16 @@ func (state DKGEndState) String() string {
 }
 
 // DKGIndexMap completely describes the DKG committee 𝒟 of size |𝒟| = n.
+//
+// Formal specification:
+//   - If n parties are authorized to participate in the DKG, DKGIndexMap must contain exactly n
+//     elements, i.e. n = len(DKGIndexMap)
+//   - The values in DKGIndexMap must form the set {0, 1, …, n-1}, as required by the low level cryptography
+//     module (convention simplifying the implementation).
+//
 // Flow's random beacon utilizes a threshold signature scheme run by the committee 𝒟.
-// In the formal cryptographic protocol for a threshold signature with n parties,
-// the individual participants are identified by n public distinct non-negative integers, or simply indices.
+// In the formal cryptographic protocol for a threshold signature with n parties, the
+// individual participants are identified by n public distinct non-negative integers, or simply indices.
 // These public indices are agreed upon by all participants and are used by the low-level
 // Shamir Secret Sharing [SSS].
 // In Flow, the threshold signature keys are generated by a Distributed Key Generation [DKG]. The DKG
@@ -52,12 +59,6 @@ func (state DKGEndState) String() string {
 // random beacon signature shares. Hence, the protocol level needs to map nodeIDs to the indices when
 // calling into the lower-level cryptographic primitives.
 //
-// Formal specification:
-//   - DKGIndexMap completely describes the DKG committee. If n parties are authorized to participate
-//     in the DKG, DKGIndexMap must contain exactly n elements, i.e. n = len(DKGIndexMap)
-//   - The values in DKGIndexMap must form the set {0, 1, …, n-1}, as required by the low level cryptography
-//     module (convention simplifying the implementation).
-//
 // CAUTION: It is important to cleanly differentiate between the consensus committee 𝒞, the DKG committee 𝒟
 // and the committee ℛ:
 //   - For an epoch, the consensus committee 𝒞 contains all nodes that are authorized to vote for blocks. Authority