Hashing in Blockchain

Cryptography · Axiom Academy

REAL WORLD Hashing in Blockchain How cryptographic hash functions power the most secure financial networks on Earth Imagine a ledger that no one can tamper with—not governments, not hackers, not even its creators. This is the promise of blockchain technology, and at its heart lies one elegant mathematical concept: cryptographic hashing . Since Bitcoin's launch in 2009, blockchain networks have processed over 10 trillion in transactions without a single successful alteration of confirmed records. How? By chaining together blocks of data using hash functions in a way that makes tampering mathematically detectable. Each block in a blockchain contains data, but more importantly, it contains the hash of the previous block . This creates an unbreakable chain. Notice how Block #2 includes the hash of Block #1. This is the "chain" in blockchain. If someone tries to change Block #1, its hash changes, breaking the link to Block #2. What Happens When Someone Tampers? Let's see the chain's security in action. Watch what happens if an attacker tries to change a transaction in Block #1: Mining: Finding the Golden Nonce To add a block to the blockchain, miners must find a nonce (number used once) that, when hashed with the block data, produces a hash starting with a certain number of zeros. This is called proof-of-work . Why require leading zeros in the hash? Mining Block (Target: hash starts with "0000") Why Bitcoin Uses Double SHA-256

This is the written version of the interactive lesson above. See the full Cryptography course.