function signCSR($signatureAlgorithm = 'sha1WithRSAEncryption')
    {
        if (!is_object($this->privateKey) || empty($this->dn)) {
            return false;
        }

        $origPublicKey = $this->publicKey;
        $class = get_class($this->privateKey);
        $this->publicKey = new $class();
        $this->publicKey->loadKey($this->privateKey->getPublicKey());
        $this->publicKey->setPublicKey();
        if (!($publicKey = $this->_formatSubjectPublicKey())) {
            return false;
        }
        $this->publicKey = $origPublicKey;

        $currentCert = isset($this->currentCert) ? $this->currentCert : NULL;
        $signatureSubject = isset($this->signatureSubject) ? $this->signatureSubject: NULL;

        if (isset($this->currentCert) && is_array($this->currentCert) && isset($this->currentCert['certificationRequestInfo'])) {
            $this->currentCert['signatureAlgorithm']['algorithm'] =
                $signatureAlgorithm;
            if (!empty($this->dn)) {
                $this->currentCert['certificationRequestInfo']['subject'] = $this->dn;
            }
            $this->currentCert['certificationRequestInfo']['subjectPKInfo'] = $publicKey;
        } else {
            $this->currentCert = array(
                'certificationRequestInfo' =>
                    array(
                        'version' => 'v1',
                        'subject' => $this->dn,
                        'subjectPKInfo' => $publicKey
                    ),
                'signatureAlgorithm' => array('algorithm' => $signatureAlgorithm),
                'signature'          => false // this is going to be overwritten later
            );
        }

        // resync $this->signatureSubject
        // save $certificationRequestInfo in case there are any File_ASN1_Element objects in it
        $certificationRequestInfo = $this->currentCert['certificationRequestInfo'];
        $this->loadCSR($this->saveCSR($this->currentCert));

        $result = $this->_sign($this->privateKey, $signatureAlgorithm);
        $result['certificationRequestInfo'] = $certificationRequestInfo;

        $this->currentCert = $currentCert;
        $this->signatureSubject = $signatureSubject;

        return $result;
    }