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Glossary Security

Hash

A hash is the fixed-length fingerprint a hash function computes from any input; the same input always gives the same hash, and the input cannot practically be recovered from it.

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In more detail

Hashes verify that data has not changed, identify duplicate files and are the building block of signatures and password storage. SHA-256 is the usual secure choice; MD5 and SHA-1 are broken for security use. A hash is not encryption: there is no key and no way back.

Example

The SHA-256 hash of hello is 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824. Make your own with the Hash Generator.

Try these tools

Hash Generator

Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text, computed locally with the Web Crypto API.

File Checksum Calculator

Calculate MD5, SHA-1, SHA-256, SHA-384, SHA-512 and CRC-32 checksums of one or many files and compare them with a published value.

See also

  • Glossary Salt
    A salt is a unique random value added to a password before hashing, so that identical passwords produce different hashes.
  • Glossary HMAC
    HMAC (hash-based message authentication code) is a hash computed with a secret key.
  • Glossary Checksum
    A checksum is a small value calculated from a block of data and used to detect accidental errors when the data is stored or sent.
  • Guide How Hashing Works
    What a hash function does, the avalanche effect shown with real SHA-256 output, which algorithms are still safe, HMAC.
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