Lightweight cryptography has been very important for the last few years. It became one the most important block of a secure embedded systems because it has been a strong requirement for any resource constrained devices, and has several features like, it consumes only less power, less memory, etc. This paper is a survey of various lightweight block ciphers such as PRESENT, GIFT, RECTANGLE, PICO and LED. The strength and weaknesses of each algorithm and the several attacks acting on them is also summarized.