phpseclib\System\SSH\Agent\Identity::sign PHP Метод

    function sign($message, $padding = RSA::PADDING_PKCS1)
    {
        if ($padding != RSA::PADDING_PKCS1 && $padding != RSA::PADDING_RELAXED_PKCS1) {
            throw new UnsupportedAlgorithmException('ssh-agent can only create PKCS1 signatures');
        }
        // the last parameter (currently 0) is for flags and ssh-agent only defines one flag (for ssh-dss): SSH_AGENT_OLD_SIGNATURE
        $packet = pack('CNa*Na*N', Agent::SSH_AGENTC_SIGN_REQUEST, strlen($this->key_blob), $this->key_blob, strlen($message), $message, 0);
        $packet = pack('Na*', strlen($packet), $packet);
        if (strlen($packet) != fputs($this->fsock, $packet)) {
            throw new \RuntimeException('Connection closed during signing');
        }
        $length = current(unpack('N', fread($this->fsock, 4)));
        $type = ord(fread($this->fsock, 1));
        if ($type != Agent::SSH_AGENT_SIGN_RESPONSE) {
            throw new \RuntimeException('Unable to retrieve signature');
        }
        $signature_blob = fread($this->fsock, $length - 1);
        // the only other signature format defined - ssh-dss - is the same length as ssh-rsa
        // the + 12 is for the other various SSH added length fields
        return substr($signature_blob, strlen('ssh-rsa') + 12);
    }