The blockchain as a set of nodes

Ethereum is a decentralized platform, which means that two or more nodes work together in a coordinated fashion to achieve a common outcome in a way that the end user sees as a single operation. A node performs various types of functions depending on the role it decides to take. It can propose and validate transactions with mining software to achieve consensus while securing the blockchain using the proof-of-work (PoW) protocol or be a light-weight node that performs payment verification and many other tasks that can be done with limited resources.

The Ethereum blockchain is based on Bitcoin, since the system created by Satoshi Nakamoto is a very robust decentralized solution. In fact, it uses a system to execute decentralized code using opcodes that can process basic instructions on top of a network of hundreds of thousands of computers in a safe manner. They must be simple to preserve security above all.

Although both blockchains are quite similar in their systems, they have noticeable differences, such as the following:

• Bitcoin and Ethereum use PoW to generate blocks, while Ethereum intends to move to PoS as the block generation system in the future to avoid wasting computational power.
• Ethereum uses the Ethash algorithm, while Bitcoin uses SHA256 for processing transactions and generating blocks.
• Ethereum's block time is about 15 seconds, which is about 100 times faster than Bitcoin's. This gives people better confirmation times.

The Ethereum blockchain is decentralized and distributed, which means that the connected nodes have several relationships with each other independently, while running the same software at different locations. This is very important to guarantee the unstoppable aspect of the blockchain. Here what each term means:

• Decentralized network: This is a network of computers running without a single point of control, no entity controls the entire system, and each node is connected to other nodes directly in a peer-to-peer (P2P) relationship. If the blockchain wasn't decentralized, some government or entity could locate the main controller node and stop the entire system immediately.
• Distributed network: This is a network where many different computers run on different locations with the same software. If the blockchain wasn't distributed, some entity could go to where all the nodes are located and stop the entire operation because they are all in the same place, so none are safe from such an attack.

You can see in the following diagram how the structure of these types of technologies connect nodes together so that they can communicate with complete security, in their own way, since it's often a confusing point when trying to understand the differences between distributed and decentralized systems:

Those two characteristics give the Ethereum network the capacity to work without having to rely on anybody, because thousands of nodes are able to communicate between each other in a secured and independent fashion. Notice that Ethereum is a completely open blockchain, meaning that anybody is free to join and participate in the decisions that take place, such as block creation and transaction processing. It allows people to join the network of nodes as a participant without any requirements, since the entire structure is secured by cryptographically-safe algorithms.

Nodes can work together or become malicious by executing unexpected code. Those that exhibit arbitrary behavior are known as Byzantine nodes. The main goal is to create a system where nodes cooperate even in the worst situations, with fault-tolerance protections in place to avoid breaking the entire structure. But how do they work together if the nodes making the blockchain can behave randomly because they are Byzantine nodes?

At the end of the day, it's a group of computers working voluntarily toward the same objective. Nothing stops them from doing unexpected actions. That's where one of the most interesting problems that blockchain is facing lies. There are several solutions, but research is still being done to obtain a perfect balance between performance and security in a decentralized system.