Bitcoin Universe · Model 19

The SHA-256 hashing machine

A hash is a fingerprint for data: the same input always gives the same fingerprint, and the smallest change gives a completely different one. Type some harmless text and watch the machine compute a real SHA-256.

Real SHA-256 · simplified round drawing

Text

Harmless demonstration text only. Never type a password, recovery phrase or private key into any website.

Hash ()

Compare with

Bitcoin's double SHA-256 (SHA-256d)

What a hash is, and is not

Padding

The 0x80 marker, the current round, and digest bits that changed The 64-bit length field

Real algorithm, simplified drawing. Every value shown is computed with SHA-256 as specified in FIPS 180-4 and checked against the official test vectors. The register wheels only point at each word's top byte and the rounds are summarised as T1, T2 and a shift; the bitwise functions (Σ, σ, Ch, Maj) are not drawn individually. Hashing is not encryption: there is no key and nothing to decrypt. Input is limited to 200 characters and is only used in your browser.