Blockchain secures digital identities by creating a tamper-proof ledger where each transaction is recorded in a decentralized manner. Each block contains a hash of the previous block, ensuring an immutable chain. Users have control over their private keys, required for transaction validation, enhancing privacy and reducing the risk of identity theft. Additionally, smart contracts can automate verification processes, ensuring only authorized parties access identity-related data. This framework fosters trust and transparency while enabling secure digital interactions in various sectors.