Hash
cryptography · security
A fixed-length digital fingerprint calculated from data.
- Also known as
- cryptographic hash, digest, message digest
1.concept
A hash is a digital fingerprint calculated from data. With the same hash function, the same input gives the same output; a small edit usually produces a very different fingerprint. It helps check whether data matches, but it does not hide the data the way encryption does.
2.properties
Useful hash functions are preimage-resistant, second-preimage-resistant, collision-resistant, fast to verify, and well distributed. Hashing is not encryption: a hash is designed for verification, not recovery of the original message.
3.uses
Blockchains use hashes to link blocks, summarize transaction sets, derive identifiers, and define proof-of-work targets. Wallet software also hashes transaction data before signing it.
The SHA-256 definition explains the hash function used by Bitcoin and Bitcoin Cash. You can also change a message and compare its fingerprint in the homepage hash playground.
Technical reference: NIST’s Secure Hash Standard specifies SHA-256 and related hash functions.
Related terms
Proof of Work (PoW)
→A consensus mechanism that makes block production require verifiable computational work.
mining · blockchain · consensus
Hash rate
→The number of proof-of-work hash attempts performed per second by mining hardware or an entire network.
mining · security
Entropy
→Entropy is the randomness used to generate secure wallet seeds, private keys, and nonces in cryptographic systems.
cryptography · security
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