To prevent centralization and maintain decentralization in blockchain and cryptocurrency, the following measures can be taken:

1. _Decentralized governance_: Implement decentralized governance models that allow all stakeholders to participate in decision-making.

2. _Node decentralization_: Encourage a large number of nodes to operate on the network, making it difficult for any single entity to control.

3. _Validator decentralization_: Ensure that validators are diverse and decentralized, preventing any single entity from dominating the validation process.

4. _Stake decentralization_: Implement mechanisms that prevent any single entity from controlling a majority of the stake in the network.

5. _Open-source code_: Make the code open-source, allowing anyone to review, modify, and distribute it.

6. _Community engagement_: Foster a strong community that promotes decentralization and prevents centralization.

7. _Incentive structures_: Design incentive structures that encourage decentralization and discourage centralization.

8. _Anti-centralization algorithms_: Implement algorithms that detect and prevent centralization.

9. _Decentralized data storage_: Use decentralized data storage solutions to prevent data centralization.

10. _Regular audits and monitoring_: Regularly audit and monitor the network to detect and prevent centralization.

By implementing these measures, decentralization can be maintained, ensuring a robust, resilient, and democratic blockchain and cryptocurrency ecosystem.