prysm-pulse/crypto/bls/blst/public_key.go

//go:build ((linux && amd64) || (linux && arm64) || (darwin && amd64) || (darwin && arm64) || (windows && amd64)) && !blst_disabled

package blst

import (
	"fmt"

	"github.com/pkg/errors"
	"github.com/prysmaticlabs/prysm/v5/cache/nonblocking"
	fieldparams "github.com/prysmaticlabs/prysm/v5/config/fieldparams"
	"github.com/prysmaticlabs/prysm/v5/config/params"
	"github.com/prysmaticlabs/prysm/v5/crypto/bls/common"
)

var maxKeys = 2_000_000
var pubkeyCache *nonblocking.LRU[[48]byte, common.PublicKey]

// PublicKey used in the BLS signature scheme.
type PublicKey struct {
	p *blstPublicKey
}

// PublicKeyFromBytes creates a BLS public key from a  BigEndian byte slice.
func PublicKeyFromBytes(pubKey []byte) (common.PublicKey, error) {
	return publicKeyFromBytes(pubKey, true)
}

func publicKeyFromBytes(pubKey []byte, cacheCopy bool) (common.PublicKey, error) {
	if len(pubKey) != params.BeaconConfig().BLSPubkeyLength {
		return nil, fmt.Errorf("public key must be %d bytes", params.BeaconConfig().BLSPubkeyLength)
	}
	newKey := (*[fieldparams.BLSPubkeyLength]byte)(pubKey)
	if cv, ok := pubkeyCache.Get(*newKey); ok {
		if cacheCopy {
			return cv.Copy(), nil
		}
		return cv, nil
	}
	// Subgroup check NOT done when decompressing pubkey.
	p := new(blstPublicKey).Uncompress(pubKey)
	if p == nil {
		return nil, errors.New("could not unmarshal bytes into public key")
	}
	// Subgroup and infinity check
	if !p.KeyValidate() {
		// NOTE: the error is not quite accurate since it includes group check
		return nil, common.ErrInfinitePubKey
	}
	pubKeyObj := &PublicKey{p: p}
	copiedKey := pubKeyObj.Copy()
	cacheKey := *newKey
	pubkeyCache.Add(cacheKey, copiedKey)
	return pubKeyObj, nil
}

// AggregatePublicKeys aggregates the provided raw public keys into a single key.
func AggregatePublicKeys(pubs [][]byte) (common.PublicKey, error) {
	if len(pubs) == 0 {
		return nil, errors.New("nil or empty public keys")
	}
	agg := new(blstAggregatePublicKey)
	mulP1 := make([]*blstPublicKey, 0, len(pubs))
	for _, pubkey := range pubs {
		pubKeyObj, err := publicKeyFromBytes(pubkey, false)
		if err != nil {
			return nil, err
		}
		mulP1 = append(mulP1, pubKeyObj.(*PublicKey).p)
	}
	// No group check needed here since it is done in PublicKeyFromBytes
	// Note the checks could be moved from PublicKeyFromBytes into Aggregate
	// and take advantage of multi-threading.
	agg.Aggregate(mulP1, false)
	return &PublicKey{p: agg.ToAffine()}, nil
}

// Marshal a public key into a LittleEndian byte slice.
func (p *PublicKey) Marshal() []byte {
	return p.p.Compress()
}

// Copy the public key to a new pointer reference.
func (p *PublicKey) Copy() common.PublicKey {
	np := *p.p
	return &PublicKey{p: &np}
}

// IsInfinite checks if the public key is infinite.
func (p *PublicKey) IsInfinite() bool {
	zeroKey := new(blstPublicKey)
	return p.p.Equals(zeroKey)
}

// Equals checks if the provided public key is equal to
// the current one.
func (p *PublicKey) Equals(p2 common.PublicKey) bool {
	return p.p.Equals(p2.(*PublicKey).p)
}

// Aggregate two public keys.
func (p *PublicKey) Aggregate(p2 common.PublicKey) common.PublicKey {
	agg := new(blstAggregatePublicKey)
	// No group check here since it is checked at decompression time
	agg.Add(p.p, false)
	agg.Add(p2.(*PublicKey).p, false)
	p.p = agg.ToAffine()

	return p
}

// AggregateMultiplePubkeys aggregates the provided decompressed keys into a single key.
func AggregateMultiplePubkeys(pubkeys []common.PublicKey) common.PublicKey {
	mulP1 := make([]*blstPublicKey, 0, len(pubkeys))
	for _, pubkey := range pubkeys {
		mulP1 = append(mulP1, pubkey.(*PublicKey).p)
	}
	agg := new(blstAggregatePublicKey)
	// No group check needed here since it is done in PublicKeyFromBytes
	// Note the checks could be moved from PublicKeyFromBytes into Aggregate
	// and take advantage of multi-threading.
	agg.Aggregate(mulP1, false)
	return &PublicKey{p: agg.ToAffine()}
}