Blockchain and distributed ledger technology is an innovative and continuously evolving technology. This technology has far reaching security implications beyond just the financial services industries. Thanks to cryptocurrencies, blockchain technology has proven its relevance and increases security for data exchanges and immutable storage of data related to transactions. However, this does not mean the technology is beyond attacks and hacks -- like the dreaded 51% attack. The CSA Blockchain Working Group's goal is to investigate and document various forms of blockchain technology, relevant use cases, and security implications. The Blockchain Working Group is dedicated to producing useable content to educate the industry on this radical technology.