Hash / Hash Function
Cryptography● Common
A cryptographic function producing a fixed-size output (digest) from arbitrary input. Bitcoin uses SHA-256 extensively: double-SHA256 for block headers and transaction IDs, SHA-256 in address derivation, HMAC-SHA512 for HD key derivation. Properties: deterministic, fast, collision-resistant, preimage-resistant, avalanche effect.
Technical Notes
SHA-256 outputs 256 bits (32 bytes). Double-SHA256: SHA256(SHA256(x)) used to prevent length extension attacks. RIPEMD-160 used after SHA-256 for shorter address hashes. TXID = double-SHA256 of serialized tx (reversed for display). Block hash = double-SHA256 of 80-byte header.
Metadata
Visibility: Public
Created:1/3/2026by System