public function setEncryptCertificate($recipientCerts, $cipher = null)
    {
        if (is_array($recipientCerts)) {
            $this->encryptCert = [];

            foreach ($recipientCerts as $cert) {
                $this->encryptCert[] = 'file://'.str_replace('\\', '/', realpath($cert));
            }
        } else {
            $this->encryptCert = 'file://'.str_replace('\\', '/', realpath($recipientCerts));
        }

        if (null !== $cipher) {
            $this->encryptCipher = $cipher;
        }

        return $this;
    }