The implementation of internet of things is plagued by problems such as security and scalability. It is a very heterogeneous environment and overcoming these hurdles is therefore not an easy feat. A concept of using the decentralized and secure nature of the blockchain technology to combat these problems have been identified. However the stark contrast of blockchain technology being resource hungry and internet of things devices being resource depraved is among other things a new hurdle that is introduced. This systematic literature study aimed to identify problems that a rose when trying to merge these technologies while focusing on the authentication aspect.Smart contracts play a huge role in making most of the identified solutions at least feasible to implement on a larger scale. While most systems have solved the authentication problem the major problems of the blockchain adaptation for internet of things remains unsolved. Three solutions were identified that really try to combat these problems by changing the blockchain technology at its core while the rest feel like they are trying to do the best with what is available and falls short in some major way.