key.go
func GenerateEKeyPair(curveName string) ([]byte, GenSharedKey, error) {
	var curve elliptic.Curve

	switch curveName {
	case "P-256":
		curve = elliptic.P256()
	case "P-384":
		curve = elliptic.P384()
	case "P-521":
		curve = elliptic.P521()
	}

	priv, x, y, err := elliptic.GenerateKey(curve, rand.Reader)
	if err != nil {
		return nil, nil, err
	}

	pubKey := elliptic.Marshal(curve, x, y)

	done := func(theirPub []byte) ([]byte, error) {
		// Verify and unpack node's public key.
		x, y := elliptic.Unmarshal(curve, theirPub)
		if x == nil {
			return nil, fmt.Errorf("malformed public key: %d %v", len(theirPub), theirPub)
		}

		if !curve.IsOnCurve(x, y) {
			return nil, errors.New("invalid public key")
		}

		// Generate shared secret.
		secret, _ := curve.ScalarMult(x, y, priv)

		return secret.Bytes(), nil
	}

	return pubKey, done, nil
}
func GenerateEKeyPair(curveName string) ([]byte, GenSharedKey, error) {
	var curve elliptic.Curve

	switch curveName {
	case "P-256":
		curve = elliptic.P256()
	case "P-384":
		curve = elliptic.P384()
	case "P-521":
		curve = elliptic.P521()
	}

	priv, x, y, err := elliptic.GenerateKey(curve, rand.Reader)
	if err != nil {
		return nil, nil, err
	}

	pubKey := elliptic.Marshal(curve, x, y)

	done := func(theirPub []byte) ([]byte, error) {
		// Verify and unpack node's public key.
		x, y := elliptic.Unmarshal(curve, theirPub)
		if x == nil {
			return nil, fmt.Errorf("malformed public key: %d %v", len(theirPub), theirPub)
		}

		if !curve.IsOnCurve(x, y) {
			return nil, errors.New("invalid public key")
		}

		// Generate shared secret.
		secret, _ := curve.ScalarMult(x, y, priv)

		return secret.Bytes(), nil
	}

	return pubKey, done, nil
}
// GenerateEKeyPair returns an ephemeral public key and returns a function that will compute
// the shared secret key.  Used in the identify module.
//
// Focuses only on ECDH now, but can be made more general in the future.