...by Daniel Szego
"Simplicity is the ultimate sophistication."
Leonardo da Vinci

Saturday, September 1, 2018

How to implement a Blockchain from scratch - block and blockchain objects

Building up a blockhcain archtiecture, two of the most important roles are certainly the blocks and the blockchain. At the implementation at least three important scenarios have to be taken into account:
- Mining: at mining, the miner creates a brand new block, adds the transactions to the block from the transaction pool and solves some cryptographic puzzle. As the block is created correctly it will be added to the local blockchain and will be communicated on the network with the help of a gossip protocol. 
- Synchronization: at synchronization, the blocks are queried from the network one by one, they are validated and added to the chain. At synchronization, there is not necessarily a forking strategy, the blocks can be queried based on the block id which can be provided as on consistent set of the chain. Similarly, the other side of the synchronization is to provide a set of transaction id-s which is regarded as the longest consistent blockchain. 
- Gossiping blocks: If the node receives a block on the network, first of all the network should already by synchronized. if we receive a new block, it must be validated and a fork resolution algorithms has to be executed as well. If the block extends the longest chain, the block should be added to the longest chain. If a block extends one of the alternative chains, it can be added to the alternative chain and it must be decided if we have a new chain longest chain. There might be the case, that the block can not be added to the chain at all, if so it can be added to a pool of orphaned blocks. Last but not least, there might be the situation as the block can not be added to the chain alone, but only with the help of another block that is already in the pool of orphaned blocks.