decToHex = function(dec, bytes) {
    var hex = "",
        i;
    for (i = 0; i < bytes; i++) {
        hex += String.fromCharCode(dec & 0xff);
        dec = dec >>> 8;
    }
    return hex;
}
Transform an integer into a string in hexadecimal.
@private
@param {number} dec the number to convert.
@param {number} bytes the number of bytes to generate.
@returns {string} the result.