Hash in Blockchain: How SHA-256 Secures Bitcoin Transactions
How Bitcoin uses SHA-256 in proof of work, transaction IDs, and block chaining — and why the math makes the chain tamper-proof.
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Tags: security, cryptography, blockchain
Hashing in Blockchain: Proof of Work, Block Headers, and Merkle Roots Bitcoin and other proof-of-work blockchains are built almost entirely on a single cryptographic primitive: the SHA-256 hash function. Understanding how hashing is used in blockchain reveals why these systems are tamper-evident, how mining works, and why "cryptocurrency" is really "hash-computation currency." This guide dissects the roles of hashing in Bitcoin specifically, as the most studied example. The Bitcoin Block Structure A Bitcoin block consists of a header and a list of transactions. The header is only 80 bytes: The block hash is: — this double-SHA256 provides extra protection against certain length-extension attacks on SHA-256. Double SHA-256 Bitcoin uses SHA-256 applied twice (often written as SHA256d or…
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