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package hybrid
import (
"crypto/ecdh"
cryptoRand "crypto/rand"
"github.com/cloudflare/circl/kem"
"github.com/cloudflare/circl/xof"
)
type cPublicKey struct {
scheme cScheme
key *ecdh.PublicKey
}
type cPrivateKey struct {
scheme cScheme
key *ecdh.PrivateKey
}
type cScheme struct {
curve ecdh.Curve
}
var p256Kem = &cScheme{ecdh.P256()}
func (sch cScheme) Name() string {
switch sch.curve {
case ecdh.P256():
return "P-256"
case ecdh.P384():
return "P-384"
case ecdh.P521():
return "P-521"
default:
panic("unsupported curve")
}
}
func (sch cScheme) PublicKeySize() int {
switch sch.curve {
case ecdh.P256():
return 65
case ecdh.P384():
return 97
case ecdh.P521():
return 133
default:
panic("unsupported curve")
}
}
func (sch cScheme) PrivateKeySize() int {
switch sch.curve {
case ecdh.P256():
return 32
case ecdh.P384():
return 48
case ecdh.P521():
return 66
default:
panic("unsupported curve")
}
}
func (sch cScheme) SeedSize() int {
return sch.PrivateKeySize()
}
func (sch cScheme) SharedKeySize() int {
return sch.PrivateKeySize()
}
func (sch cScheme) CiphertextSize() int {
return sch.PublicKeySize()
}
func (sch cScheme) EncapsulationSeedSize() int {
return sch.SeedSize()
}
func (sk *cPrivateKey) Scheme() kem.Scheme { return sk.scheme }
func (pk *cPublicKey) Scheme() kem.Scheme { return pk.scheme }
func (sk *cPrivateKey) MarshalBinary() ([]byte, error) {
return sk.key.Bytes(), nil
}
func (sk *cPrivateKey) Equal(other kem.PrivateKey) bool {
oth, ok := other.(*cPrivateKey)
if !ok {
return false
}
if oth.scheme != sk.scheme {
return false
}
return oth.key.Equal(sk.key)
}
func (sk *cPrivateKey) Public() kem.PublicKey {
pk := sk.key.PublicKey()
return &cPublicKey{scheme: sk.scheme, key: pk}
}
func (pk *cPublicKey) Equal(other kem.PublicKey) bool {
oth, ok := other.(*cPublicKey)
if !ok {
return false
}
if oth.scheme != pk.scheme {
return false
}
return oth.key.Equal(pk.key)
}
func (pk *cPublicKey) MarshalBinary() ([]byte, error) {
return pk.key.Bytes(), nil
}
func (sch cScheme) GenerateKeyPair() (kem.PublicKey, kem.PrivateKey, error) {
seed := make([]byte, sch.SeedSize())
_, err := cryptoRand.Read(seed)
if err != nil {
return nil, nil, err
}
pk, sk := sch.DeriveKeyPair(seed)
return pk, sk, nil
}
func (sch cScheme) DeriveKeyPair(seed []byte) (kem.PublicKey, kem.PrivateKey) {
if len(seed) != sch.SeedSize() {
panic(kem.ErrSeedSize)
}
h := xof.SHAKE256.New()
_, _ = h.Write(seed)
privKey, err := sch.curve.GenerateKey(h)
if err != nil {
panic(err)
}
pubKey := privKey.PublicKey()
sk := cPrivateKey{scheme: sch, key: privKey}
pk := cPublicKey{scheme: sch, key: pubKey}
return &pk, &sk
}
func (sch cScheme) Encapsulate(pk kem.PublicKey) (ct, ss []byte, err error) {
seed := make([]byte, sch.EncapsulationSeedSize())
_, err = cryptoRand.Read(seed)
if err != nil {
return
}
return sch.EncapsulateDeterministically(pk, seed)
}
func (pk *cPublicKey) X(sk *cPrivateKey) []byte {
if pk.scheme != sk.scheme {
panic(kem.ErrTypeMismatch)
}
sharedKey, err := sk.key.ECDH(pk.key)
if err != nil {
// ECDH cannot fail for NIST curves as NewPublicKey rejects
// invalid points and the point in infinity, and NewPrivateKey
// rejects invalid scalars and the zero value.
panic(err)
}
return sharedKey
}
func (sch cScheme) EncapsulateDeterministically(
pk kem.PublicKey, seed []byte,
) (ct, ss []byte, err error) {
if len(seed) != sch.EncapsulationSeedSize() {
return nil, nil, kem.ErrSeedSize
}
pub, ok := pk.(*cPublicKey)
if !ok || pub.scheme != sch {
return nil, nil, kem.ErrTypeMismatch
}
pk2, sk2 := sch.DeriveKeyPair(seed)
ss = pub.X(sk2.(*cPrivateKey))
ct, _ = pk2.MarshalBinary()
return
}
func (sch cScheme) Decapsulate(sk kem.PrivateKey, ct []byte) ([]byte, error) {
if len(ct) != sch.CiphertextSize() {
return nil, kem.ErrCiphertextSize
}
priv, ok := sk.(*cPrivateKey)
if !ok || priv.scheme != sch {
return nil, kem.ErrTypeMismatch
}
pk, err := sch.UnmarshalBinaryPublicKey(ct)
if err != nil {
return nil, err
}
ss := pk.(*cPublicKey).X(priv)
return ss, nil
}
func (sch cScheme) UnmarshalBinaryPublicKey(buf []byte) (kem.PublicKey, error) {
if len(buf) != sch.PublicKeySize() {
return nil, kem.ErrPubKeySize
}
key, err := sch.curve.NewPublicKey(buf)
if err != nil {
return nil, err
}
return &cPublicKey{sch, key}, nil
}
func (sch cScheme) UnmarshalBinaryPrivateKey(buf []byte) (kem.PrivateKey, error) {
if len(buf) != sch.PrivateKeySize() {
return nil, kem.ErrPrivKeySize
}
key, err := sch.curve.NewPrivateKey(buf)
if err != nil {
return nil, err
}
return &cPrivateKey{sch, key}, nil
}
|
