With the spread of Internet of Things (IoT), ensuring security and privacy proves essential. However, given the limited computation resources of IoT objects, the mechanisms and techniques used to secure data exchange in these environments should consider many constraints such as power consumption, size, execution time … etc. To cope with these constraints, new lightweight encryption systems have been proposed. This work is intended to compare some recently proposed lightweight cryptosystem in order to identify and suggest the necessary recommendations to achieve an ultra-lightweight cryptosystem adapted to IoT environment.