Add Aggregated Public Key Method (#14178)

* Add aggregated key method

* Gazelle

* Manu's Review

beacon-chain/core/blocks/signature.go

@@ -204,12 +204,7 @@ func createAttestationSignatureBatch(
 			return nil, err
 		}
 		indices := ia.GetAttestingIndices()
-		pubkeys := make([][]byte, len(indices))
-		for i := 0; i < len(indices); i++ {
-			pubkeyAtIdx := beaconState.PubkeyAtIndex(primitives.ValidatorIndex(indices[i]))
-			pubkeys[i] = pubkeyAtIdx[:]
-		}
-		aggP, err := bls.AggregatePublicKeys(pubkeys)
+		aggP, err := beaconState.AggregateKeyFromIndices(indices)
 		if err != nil {
 			return nil, err
 		}

beacon-chain/state/BUILD.bazel

@@ -13,6 +13,7 @@ go_library(
         "//config/fieldparams:go_default_library",
         "//consensus-types/interfaces:go_default_library",
         "//consensus-types/primitives:go_default_library",
+        "//crypto/bls:go_default_library",
         "//proto/engine/v1:go_default_library",
         "//proto/prysm/v1alpha1:go_default_library",
         "@com_github_prometheus_client_golang//prometheus:go_default_library",

beacon-chain/state/interfaces.go

@@ -11,6 +11,7 @@ import (
 	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/interfaces"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
+	"github.com/prysmaticlabs/prysm/v5/crypto/bls"
 	enginev1 "github.com/prysmaticlabs/prysm/v5/proto/engine/v1"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 )
@@ -129,6 +130,7 @@ type ReadOnlyValidators interface {
 	ValidatorIndexByPubkey(key [fieldparams.BLSPubkeyLength]byte) (primitives.ValidatorIndex, bool)
 	PublicKeys() ([][fieldparams.BLSPubkeyLength]byte, error)
 	PubkeyAtIndex(idx primitives.ValidatorIndex) [fieldparams.BLSPubkeyLength]byte
+	AggregateKeyFromIndices(idxs []uint64) (bls.PublicKey, error)
 	NumValidators() int
 	ReadFromEveryValidator(f func(idx int, val ReadOnlyValidator) error) error
 }

beacon-chain/state/state-native/BUILD.bazel

@@ -68,6 +68,7 @@ go_library(
         "//consensus-types/primitives:go_default_library",
         "//container/multi-value-slice:go_default_library",
         "//container/slice:go_default_library",
+        "//crypto/bls:go_default_library",
         "//crypto/hash:go_default_library",
         "//encoding/bytesutil:go_default_library",
         "//encoding/ssz:go_default_library",
@@ -141,6 +142,7 @@ go_test(
         "//consensus-types/interfaces:go_default_library",
         "//consensus-types/primitives:go_default_library",
         "//container/trie:go_default_library",
+        "//crypto/bls:go_default_library",
         "//crypto/rand:go_default_library",
         "//encoding/bytesutil:go_default_library",
         "//proto/engine/v1:go_default_library",

beacon-chain/state/state-native/getters_validator.go

@@ -9,6 +9,7 @@ import (
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	consensus_types "github.com/prysmaticlabs/prysm/v5/consensus-types"
 	"github.com/prysmaticlabs/prysm/v5/consensus-types/primitives"
+	"github.com/prysmaticlabs/prysm/v5/crypto/bls"
 	"github.com/prysmaticlabs/prysm/v5/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/v5/runtime/version"
@@ -223,6 +224,36 @@ func (b *BeaconState) PubkeyAtIndex(idx primitives.ValidatorIndex) [fieldparams.
 	return bytesutil.ToBytes48(v.PublicKey)
 }
 
+// AggregateKeyFromIndices builds an aggregated public key from the provided
+// validator indices.
+func (b *BeaconState) AggregateKeyFromIndices(idxs []uint64) (bls.PublicKey, error) {
+	b.lock.RLock()
+	defer b.lock.RUnlock()
+
+	pubKeys := make([][]byte, len(idxs))
+	for i, idx := range idxs {
+		var v *ethpb.Validator
+		if features.Get().EnableExperimentalState {
+			var err error
+			v, err = b.validatorsMultiValue.At(b, idx)
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			if idx >= uint64(len(b.validators)) {
+				return nil, consensus_types.ErrOutOfBounds
+			}
+			v = b.validators[idx]
+		}
+
+		if v == nil {
+			return nil, ErrNilWrappedValidator
+		}
+		pubKeys[i] = v.PublicKey
+	}
+	return bls.AggregatePublicKeys(pubKeys)
+}
+
 // PublicKeys builds a list of all validator public keys, with each key's index aligned to its validator index.
 func (b *BeaconState) PublicKeys() ([][fieldparams.BLSPubkeyLength]byte, error) {
 	b.lock.RLock()

beacon-chain/state/state-native/getters_validator_test.go

@@ -10,7 +10,9 @@ import (
 	testtmpl "github.com/prysmaticlabs/prysm/v5/beacon-chain/state/testing"
 	"github.com/prysmaticlabs/prysm/v5/config/params"
 	consensus_types "github.com/prysmaticlabs/prysm/v5/consensus-types"
+	"github.com/prysmaticlabs/prysm/v5/crypto/bls"
 	ethpb "github.com/prysmaticlabs/prysm/v5/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/v5/testing/assert"
 	"github.com/prysmaticlabs/prysm/v5/testing/require"
 	"github.com/prysmaticlabs/prysm/v5/testing/util"
 )
@@ -145,3 +147,18 @@ func TestPendingBalanceToWithdraw(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, uint64(600), ab)
 }
+
+func TestAggregateKeyFromIndices(t *testing.T) {
+	dState, _ := util.DeterministicGenesisState(t, 10)
+	pKey1 := dState.PubkeyAtIndex(3)
+	pKey2 := dState.PubkeyAtIndex(7)
+	pKey3 := dState.PubkeyAtIndex(9)
+
+	aggKey, err := bls.AggregatePublicKeys([][]byte{pKey1[:], pKey2[:], pKey3[:]})
+	require.NoError(t, err)
+
+	retKey, err := dState.AggregateKeyFromIndices([]uint64{3, 7, 9})
+	require.NoError(t, err)
+
+	assert.Equal(t, true, aggKey.Equals(retKey), "unequal aggregated keys")
+}