ATX v2 (for ATX merge) (#5785)

## Motivation

Proposal of the new ATX version to support the atx merging.

activation/wire/challenge_v2.go

@@ -0,0 +1,43 @@
+package wire
+
+import (
+	"go.uber.org/zap/zapcore"
+
+	"github.com/spacemeshos/go-spacemesh/codec"
+	"github.com/spacemeshos/go-spacemesh/common/types"
+	"github.com/spacemeshos/go-spacemesh/hash"
+)
+
+//go:generate scalegen
+
+// NIPostChallengeV2 collects information needed to generate a PoET challenge.
+// It's hash is the challenge registered in the PoET.
+type NIPostChallengeV2 struct {
+	PublishEpoch     types.EpochID
+	PrevATXID        types.ATXID
+	PositioningATXID types.ATXID
+	CommitmentATXID  *types.ATXID
+	InitialPost      *PostV1
+}
+
+// Hash serializes the NIPostChallenge and returns its hash.
+// The serialized challenge is first prepended with a byte 0x00, and then hashed
+// for second preimage resistance of poet membership merkle tree.
+func (c *NIPostChallengeV2) Hash() types.Hash32 {
+	ncBytes := codec.MustEncode(c)
+	return hash.Sum([]byte{0x00}, ncBytes)
+}
+
+func (c *NIPostChallengeV2) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
+	if c == nil {
+		return nil
+	}
+	encoder.AddUint32("PublishEpoch", c.PublishEpoch.Uint32())
+	encoder.AddString("PrevATXID", c.PrevATXID.String())
+	encoder.AddString("PositioningATX", c.PositioningATXID.String())
+	if c.CommitmentATXID != nil {
+		encoder.AddString("CommitmentATX", c.CommitmentATXID.String())
+	}
+	encoder.AddObject("InitialPost", c.InitialPost)
+	return nil
+}

activation/wire/wire_v2.go

@@ -0,0 +1,87 @@
+package wire
+
+import "github.com/spacemeshos/go-spacemesh/common/types"
+
+//go:generate scalegen
+
+type ActivationTxV2 struct {
+	PublishEpoch   types.EpochID
+	PositioningATX types.ATXID
+
+	// Must be present in the initial ATX.
+	// Nil in subsequent ATXs unless smesher wants to change it.
+	// If Nil, the value is inferred from the previous ATX of this smesher.
+	// It's not allowed to pass the same coinbase as already used by the previous ATX
+	// to avoid spamming the network with redundant information.
+	Coinbase *types.Address
+
+	// only present in initial ATX
+	Initial      *InitialAtxPartsV2
+	PreviousATXs []types.ATXID `scale:"max=256"`
+	NiPosts      []NiPostsV2   `scale:"max=2"`
+
+	// The VRF nonce must be valid for the collected space of all included IDs.
+	// only present when:
+	// - the nonce changed (included more/heavier IDs)
+	// - it's an initial ATX
+	VRFNonce *uint64
+
+	// The list of marriages with other IDs.
+	// A marriage is permanent and cannot be revoked or repeated.
+	// All new IDs that are married to this ID are added to the equivocation set
+	// that this ID belongs to.
+	Marriages []MarriageCertificate `scale:"max=256"`
+
+	// The ID of the ATX containing marriage for the included IDs.
+	// Only required when the ATX includes married IDs.
+	MarriageATX *types.ATXID
+
+	Signature types.EdSignature
+}
+
+// The first PoST is always for the ATX owner.
+func (atx *ActivationTxV2) SmesherID() types.NodeID {
+	return atx.NiPosts[0].Posts[0].ID
+}
+
+type InitialAtxPartsV2 struct {
+	CommitmentATX types.ATXID
+	Post          PostV1
+	// needed make hash of the first InnerActivationTxV2 unique
+	// if the InitialPost happens to be the same for different IDs.
+	NodeID types.NodeID
+}
+
+// MarriageCertificate proves the will of ID to be married with the ID that includes this certificate.
+// A marriage allows for publishing a merged ATX, which can contain PoST for all married IDs.
+// Any ID from the marriage can publish a merged ATX on behalf of all married IDs.
+type MarriageCertificate struct {
+	ID types.NodeID
+	// Signature over the other ID that this ID marries with
+	// If Alice marries Bob, then Alice signs Bob's ID
+	// and Bob includes this certificate in his ATX.
+	Signature types.EdSignature
+}
+
+// MerkleProofV2 proves membership of multiple challenges in a PoET membership merkle tree.
+type MerkleProofV2 struct {
+	// Nodes on path from leaf to root (not including leaf)
+	Nodes       []types.Hash32 `scale:"max=32"`
+	LeafIndices []uint64       `scale:"max=256"` // support merging up to 256 IDs
+}
+
+type SubPostV2 struct {
+	ID           types.NodeID // The ID that this PoST is for.
+	PrevATXIndex uint32       // Index of the previous ATX in the `InnerActivationTxV2.PreviousATXs` slice
+	Post         PostV1
+	NumUnits     uint32
+}
+
+type NiPostsV2 struct {
+	// Single membership proof for all IDs in `Posts`.
+	// The index of ID in `Posts` is the index of the challenge in the proof (`LeafIndices`).
+	Membership MerkleProofV2
+	// The root of the PoET proof, that serves as the challenge for PoSTs.
+	Challenge types.Hash32
+	Posts     []SubPostV2 `scale:"max=256"` // support merging up to 256 IDs
+}