}
		if l := len(curvePrivateKey); l != ed25519.SeedSize {
			return nil, fmt.Errorf("x509: invalid Ed25519 private key length: %d", l)
		}
		return ed25519.NewKeyFromSeed(curvePrivateKey), nil

	case privKey.Algo.Algorithm.Equal(oidPublicKeyX25519):
		if l := len(privKey.Algo.Parameters.FullBytes); l != 0 {
			return nil, errors.New("x509: invalid X25519 private key parameters")
		}