  With the advancement of technology and subsequently the age of digital
information, online trustworthy identification has become increasingly more
important. With respect to the various data breaches and privacy regulations,
the current identity solutions are not fully optimized. In this paper, we will
take a look at several Self-Sovereign Identity solutions which are already
available. Some of them are built upon blockchain technology as this already
provides decentralised persistent data and consensus. We will explore the
emerging landscape of Self-Sovereign Identity solutions and dissect their
implementations under multiple aspect criteria to determine the necessity of
blockchain technology in this field. We conclude that blockchain technology is
not explicitly required for a Self-Sovereign Identity solution but it is a good
foundation to build up on, due to various technical advantages that the
blockchain has to offer.
