Cryptographic hashes
A hash turns data into a compact fingerprint. It helps expose changes, but it does not make the data true, secret or permanent.
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THE INTERACTIVE FIELD GUIDE
Change one block. Follow the consequences.
Edit a record, recompute a real SHA-256 digest, and discover why hash links alone do not make history immutable.
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READ THE MODEL
Assumptions & scope
- Three fictional records use a simplified JSON block format, not Bitcoin headers.
- SHA-256 is real; proof of work, validator votes and network consensus are omitted.
- Rebuilding descendants repairs local consistency, but does not make an altered chain authoritative.
National Institute of Standards and Technology · FIPS 180-4: Secure Hash Standard ↗Checked 13 Nov 2026Satoshi Nakamoto · Bitcoin: A Peer-to-Peer Electronic Cash System ↗Checked 13 Nov 2026
Understand the moving parts
All labs ↗Blocks and ordered execution
A block packages an ordered set of transactions with commitments that let other nodes verify it. Its producer proposes a result; the network still checks it.
What a blockchain adds
A blockchain joins a shared history, verifiable state transitions and a rule for choosing between competing histories. The chain of hashes is only one component.
Proof of work
Proof of work makes block production a costly search. In Bitcoin, nodes choose the valid chain with the most accumulated work, not simply the most blocks.