Blockchain technology ensures data security through its decentralized, distributed ledger system. Each block in a blockchain contains a cryptographic hash of the previous block, creating a secure, immutable chain. This means that once data is recorded, it cannot be altered without altering all subsequent blocks, requiring consensus among network participants. The decentralized nature of blockchain eliminates reliance on a single point of authority, making it resistant to fraud and unauthorized tampering. Additionally, features like encryption and smart contracts further enhance security by ensuring that transactions occur only under agreed-upon conditions, making blockchain a robust solution for secure data management.