lnd.xprv/keychain/ecdh.go
2020-05-20 09:04:05 +02:00

83 lines
2.6 KiB
Go

package keychain
import (
"crypto/sha256"
"github.com/btcsuite/btcd/btcec"
)
// NewPubKeyECDH wraps the given key of the key ring so it adheres to the
// SingleKeyECDH interface.
func NewPubKeyECDH(keyDesc KeyDescriptor, ecdh ECDHRing) *PubKeyECDH {
return &PubKeyECDH{
keyDesc: keyDesc,
ecdh: ecdh,
}
}
// PubKeyECDH is an implementation of the SingleKeyECDH interface. It wraps an
// ECDH key ring so it can perform ECDH shared key generation against a single
// abstracted away private key.
type PubKeyECDH struct {
keyDesc KeyDescriptor
ecdh ECDHRing
}
// PubKey returns the public key of the private key that is abstracted away by
// the interface.
//
// NOTE: This is part of the SingleKeyECDH interface.
func (p *PubKeyECDH) PubKey() *btcec.PublicKey {
return p.keyDesc.PubKey
}
// ECDH performs a scalar multiplication (ECDH-like operation) between the
// abstracted private key and a remote public key. The output returned will be
// the sha256 of the resulting shared point serialized in compressed format. If
// k is our private key, and P is the public key, we perform the following
// operation:
//
// sx := k*P
// s := sha256(sx.SerializeCompressed())
//
// NOTE: This is part of the SingleKeyECDH interface.
func (p *PubKeyECDH) ECDH(pubKey *btcec.PublicKey) ([32]byte, error) {
return p.ecdh.ECDH(p.keyDesc, pubKey)
}
// PrivKeyECDH is an implementation of the SingleKeyECDH in which we do have the
// full private key. This can be used to wrap a temporary key to conform to the
// SingleKeyECDH interface.
type PrivKeyECDH struct {
// PrivKey is the private key that is used for the ECDH operation.
PrivKey *btcec.PrivateKey
}
// PubKey returns the public key of the private key that is abstracted away by
// the interface.
//
// NOTE: This is part of the SingleKeyECDH interface.
func (p *PrivKeyECDH) PubKey() *btcec.PublicKey {
return p.PrivKey.PubKey()
}
// ECDH performs a scalar multiplication (ECDH-like operation) between the
// abstracted private key and a remote public key. The output returned will be
// the sha256 of the resulting shared point serialized in compressed format. If
// k is our private key, and P is the public key, we perform the following
// operation:
//
// sx := k*P
// s := sha256(sx.SerializeCompressed())
//
// NOTE: This is part of the SingleKeyECDH interface.
func (p *PrivKeyECDH) ECDH(pub *btcec.PublicKey) ([32]byte, error) {
s := &btcec.PublicKey{}
s.X, s.Y = btcec.S256().ScalarMult(pub.X, pub.Y, p.PrivKey.D.Bytes())
return sha256.Sum256(s.SerializeCompressed()), nil
}
var _ SingleKeyECDH = (*PubKeyECDH)(nil)
var _ SingleKeyECDH = (*PrivKeyECDH)(nil)