A block chain could be a group action information shared by all nodes collaborating during a system that supported the Bitcoin protocol. A full copy of a currency's block chain contains each group action ever dead within the currency. With this info, one will verify what proportion worth belonged to every address at any purpose in history. Each block contains a hash of the previous block. This has the impact of making a sequence of blocks from the genesis block to this block. Every block is absolute to come back once the previous block chronologically as a result of the previous block's hash would otherwise not be glorious. Every block is additionally computationally impractical to change once it's been within the chain for a jiffy as a result of each block once it'd even have to be regenerated. These properties square measure what create bit coins transactions irreversibly? The block chain is the main innovation of Bit coin.