Blockchain technology secures data by linking chronological blocks using unique cryptographic hashes.

Every block in the chain holds its own unique cryptographic fingerprint, called a hash, alongside the hash of the block before it. If you try to alter the data inside a block, its hash instantly changes. This breaks the link to the next block, making the tampering visible to everyone. To successfully alter the chain, you would have to recalculate the mathematical proof-of-work for every single block that follows.