#### Introduction
Censorship in blockchains is a serious issue that has generated a lot of debate in the crypto community. Depending on the nature of the blockchain, censorship may be considered an attack or a feature. In this article, we will look at censorship mechanisms, their consequences, and possible solutions to ensure the viability and security of blockchains.
#### Censorship mechanisms
In blockchains, validators play a key role in adding transactions to blocks. They have control over which transactions are included, giving them the ability to blacklist certain addresses. Transactions first go into a transaction pool, and then validators choose which ones to add to their block, which will be published.
In a scenario where censorship is performed by a single validator, some transactions may be delayed or invalidated due to time constraints. However, the danger that censorship will become more real increases when the number of validators performing this attack increases.
#### Consequences of censorship
Censorship in blockchains can lead to the following negative consequences:
1. Violation of decentralization: Censorship undermines the fundamental principle of decentralization on which blockchains are built.
2. Reduced trust: Users may lose trust in the system if their transactions are systematically rejected.
3. Economic Loss: Delayed or canceled transactions may result in financial loss for users.
#### Recommendations for eliminating censorship
To combat censorship in blockchains, you can consider the following recommendations:
1. Viability requirements: Introducing viability requirements can ensure the end-to-end transaction process and eliminate censorship. This means that all valid transactions must be included in blocks within a certain time.
2. Punishment of nodes: The protocol can punish nodes that do not create blocks in the order specified by the protocol. This may include fines or exclusion from the network.
3. Using zk-SNARKs: Zero-knowledge short knowledge arguments (zk-SNARKs) can be used to hide the identity of the sender of a transaction. This will make it difficult for validators to censor certain transactions since they will not know who the sender is.
#### Conclusion
Censorship in blockchains poses a serious threat to decentralization and trust in the system. However, by implementing liveness requirements, node penalties, and the use of zk-SNARKs, the risks of censorship can be significantly reduced and blockchains can operate more fairly and securely.
#### Link
Research on Long Range Attacks for Proof of Stake Protocols: IEEE Xplore