WIP

asset/asset.go

@@ -1033,6 +1033,9 @@ type GroupKey struct {
 
 // GroupKeyRequest contains the essential fields used to derive a group key.
 type GroupKeyRequest struct {
+	// Version is the version of the group key construction.
+	Version GroupKeyVersion
+
 	// RawKey is the raw group key before the tweak with the genesis point
 	// has been applied.
 	RawKey keychain.KeyDescriptor
@@ -2055,7 +2058,15 @@ func NewGroupKeyRequest(internalKey keychain.KeyDescriptor,
 	customTapscriptRoot fn.Option[chainhash.Hash]) (*GroupKeyRequest,
 	error) {
 
+	// Specify the group key version based on the presence of an external
+	// key.
+	var version GroupKeyVersion
+	if externalKey.IsSome() {
+		version = GroupKeyV1
+	}
+
 	req := &GroupKeyRequest{
+		Version:             version,
 		RawKey:              internalKey,
 		ExternalKey:         externalKey,
 		AnchorGen:           anchorGen,
@@ -2106,6 +2117,25 @@ func (req *GroupKeyRequest) Validate() error {
 			sha256.Size)
 	}
 
+	// Version 1 specific checks.
+	if req.Version == GroupKeyV1 {
+		tapscriptRoot, err := chainhash.NewHash(req.TapscriptRoot)
+		if err != nil {
+			return fmt.Errorf("version 1 group key request " +
+				"tapscript root must be a valid hash")
+		}
+
+		if tapscriptRoot.IsEqual(&chainhash.Hash{}) {
+			return fmt.Errorf("version 1 group key request " +
+				"tapscript root must not be all zeros")
+		}
+	}
+
+	if req.ExternalKey.IsSome() && req.Version != GroupKeyV1 {
+		return fmt.Errorf("external key can only be specified for " +
+			"version 1 group key request")
+	}
+
 	return nil
 }
 

proof/mint.go

@@ -6,11 +6,9 @@ import (
 	"fmt"
 
 	"github.com/btcsuite/btcd/btcec/v2"
-	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightninglabs/taproot-assets/asset"
 	"github.com/lightninglabs/taproot-assets/commitment"
-	"github.com/lightninglabs/taproot-assets/fn"
 )
 
 // Blob either represents a serialized proof file, including the checksum or a
@@ -388,21 +386,21 @@ func committedProofs(baseProof *Proof, tapTreeRoot *commitment.TapCommitment,
 		if newAsset.GroupKey != nil {
 			groupKey := newAsset.GroupKey
 
+			// Check if the asset is the group anchor.
 			err := groupAnchorVerifier(&newAsset.Genesis, groupKey)
 			if err == nil {
-				// TODO(ffranr): Handle custom tapscript
-				//  subtree.
-				groupReveal, err := asset.NewGroupKeyRevealV1(
-					*groupKey.RawKey.PubKey,
-					newAsset.Genesis.ID(),
-					fn.None[chainhash.Hash](),
+				// At this point, we know that the asset is the
+				// group anchor. We'll now create the group key
+				// reveal for this asset.
+				groupReveal, err := asset.NewGroupKeyReveal(
+					*groupKey, newAsset.Genesis.ID(),
 				)
 				if err != nil {
 					return nil, fmt.Errorf("unable to " +
 						"create group key reveal")
 				}
 
-				assetProof.GroupKeyReveal = &groupReveal
+				assetProof.GroupKeyReveal = groupReveal
 			}
 		}
 

tapgarden/planter.go

@@ -879,6 +879,7 @@ func buildGroupReqs(genesisPoint wire.OutPoint, assetOutputIndex uint32,
 			genTXs = append(genTXs, *genTx)
 
 			newGroupKey := &asset.GroupKey{
+				Version:       groupReq.Version,
 				RawKey:        *seedling.GroupInternalKey,
 				TapscriptRoot: seedling.GroupTapscriptRoot,
 			}
@@ -1786,11 +1787,14 @@ func (c *ChainPlanter) sealBatch(ctx context.Context, params SealParams,
 		switch {
 		case ok:
 			// Set the provided witness; it will be validated below.
+			subtreeRoot := groupReq.CustomTapscriptRoot
 			groupKey = &asset.GroupKey{
-				RawKey:        groupReq.RawKey,
-				GroupPubKey:   genTX.TweakedKey,
-				TapscriptRoot: groupReq.TapscriptRoot,
-				Witness:       groupWitness.Witness,
+				Version:             groupReq.Version,
+				RawKey:              groupReq.RawKey,
+				GroupPubKey:         genTX.TweakedKey,
+				TapscriptRoot:       groupReq.TapscriptRoot,
+				CustomTapscriptRoot: subtreeRoot,
+				Witness:             groupWitness.Witness,
 			}
 
 		default: