The blockchain trilemma is defined as the idea that it is difficult for a blockchain to be decentralized, scalable, and secure simultaneously. Blockchains can only process a certain number of transactions at a time, meaning if blockchain technology were to be adopted globally, it would result in slow transaction times, and high transaction fees. Increasing one blockchain element tends to weaken the other two, resulting in the blockchain trilemma. Below is an in depth look at each of the three blockchain elements and how they effect and interact with each other.
If a blockchain is decentralized it means that there is no one figure controlling the network. The network is open to anyone who wants to utilize it, resulting in distributed control. Decentralized networks can deter bad actors because if a user tries to change records in their favor, the other network participants will reject the fraudulent data. But, if the network is not secure, the bad actor can change data in their favor, resulting in the second part of the blockchain trilemma, security.
Centralized systems are closed, meaning, whoever is in control guarantees that the data was not interfered with. Because there is no one entity controlling a decentralized system, consensus algorithms are used as a form of security. The Proof of Work consensus algorithm, for example, requires a participating node to prove that the work they have completed and qualifies them to add new transactions to the blockchain.
Scalability refers to building a blockchain that has the bandwidth to support a large volume of transactions per second. Decentralization and security are at the heart of blockchain characteristics and tend to be focused on more than scalability. If blockchain is adopted on a larger scale, the network will be overcrowded with an influx of transactions trying to go through. Blockchain transaction speeds are limited due to the manner in which information is processed by blockchain participants.
Sharding, for example, results in splitting one blockchain into several smaller blockchains, allowing for transactions to be processed by many different ledgers, decreasing transaction time. Finding a new way to reach a consensus is another approach taken to solve the trilemma. Miners and computing power make for a secure blockchain, but a slow one. Some believe that a layer 2 blockchain is the solution. A layer 2 blockchain means that there is a sidechain, or seperate blockchain, that is connected to the main chain. Sidechains are able to operate under a unique set of rules, separate from the main chain, resulting in higher speed and scalability. There is no one solution to the blockchain trilemma, but the importance behind solving this issue, have garnered many attempts with varying results.