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package ecdh
import (
"crypto"
"io"
"golang.org/x/crypto/curve25519"
)
type curve25519ECDH struct {
ECDH
}
// NewCurve25519ECDH creates a new ECDH instance that uses djb's curve25519
// elliptical curve.
func NewCurve25519ECDH() ECDH {
return &curve25519ECDH{}
}
func (e *curve25519ECDH) GenerateKey(rand io.Reader) (crypto.PrivateKey, crypto.PublicKey, error) {
var pub, priv [32]byte
var err error
_, err = io.ReadFull(rand, priv[:])
if err != nil {
return nil, nil, err
}
priv[0] &= 248
priv[31] &= 127
priv[31] |= 64
curve25519.ScalarBaseMult(&pub, &priv)
return &priv, &pub, nil
}
func (e *curve25519ECDH) Marshal(p crypto.PublicKey) []byte {
pub := p.(*[32]byte)
return pub[:]
}
func (e *curve25519ECDH) Unmarshal(data []byte) (crypto.PublicKey, bool) {
var pub [32]byte
if len(data) != 32 {
return nil, false
}
copy(pub[:], data)
return &pub, true
}
func (e *curve25519ECDH) GenerateSharedSecret(privKey crypto.PrivateKey, pubKey crypto.PublicKey) ([]byte, error) {
var priv, pub, secret *[32]byte
priv = privKey.(*[32]byte)
pub = pubKey.(*[32]byte)
secret = new([32]byte)
curve25519.ScalarMult(secret, priv, pub)
return secret[:], nil
}