What is a blockchain? A blockchain is an operating system designed to preserve data and maintain operational consistency over a wide range of distributed networks. It can be divided into 4 stages:

Stage 1: A cryptocurrency is essentially a number recorded on a blockchain and its addition or subtraction operations.

Real-world cryptocurrencies: Bitcoin, Litecoin and Zcash

Applications: Payment and exchange

Modification: If the number is encrypted but plus and minus operation can be still executed, it will be a totally anonymous currency.

Problems to be solved in this scope:

1. Impact of consensus selection on the system

2. Economic dynamics of profit from mining

3. Joint to the flat money system

4. Problems in efficiency