In a blockchain, what ensures data integrity by linking successive blocks?

• A. The encryption algorithm
• B. Cryptographic hashes linking blocks
• C. Centralized servers
• D. Public-key encryption of blocks

Answer: (B)

Linking successive blocks with cryptographic hashes ensures data integrity across the chain. Each block includes a hash of the previous block and its own content, so the hash chain binds them together. Because hash functions are deterministic, any change to a block’s data would produce a different hash, breaking the link to the next block and making tampering obvious. Recomputing all the hashes to cover up a modified history is extremely difficult in a distributed network, which is what helps maintain an immutable ledger.

Encryption algorithms, while useful for confidentiality, don’t by themselves connect blocks to guarantee integrity. Centralized servers contradict the decentralized nature of blockchains, where integrity comes from consensus and the hash-linked chain rather than a single point of control. Public-key encryption can authenticate or protect messages, but the fundamental mechanism that ties blocks together and preserves integrity is the cryptographic hash linkage.