function begin(path, params, nonce){
    var signature = getMessageSignature(path, params, nonce);

        var headers = {
            'Content-Type': 'application/x-www-form-urlencoded',
            'Apiauth-Key': config.key,
            'Apiauth-Nonce': nonce,
            'Apiauth-Signature': signature
        };


        return rawRequest(rUrl, headers, params, method, callback);

function getMessageSignature(path, params, nonce) {
    var data_params = params;


    var postParameters  = querystring.stringify(data_params);
    var check = {}
    var path = '/api' + path + '/';

    var message = nonce + config.key + path + postParameters;

    var auth_hash = crypto.createHmac("sha256", config.secret).update(message).digest('hex').toUpperCase();
    return auth_hash;
}

var options = {
            url: url + '/',
            headers: headers,
            form: params
        };

request.post(options, function(err, res, body){
...
...
})

var form = req.form();

form.append('file', image, {
             filename: 'myfile.png',
             enctype: 'multipart/form-data'
    });

var image = new Buffer(binar_image, 'base64');