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What Is a Cryptographic Hash? SHA-256, MD5, and Hash Functions Explained

· Tags: cryptographic-hash, sha256, hash-function, cryptography, beginner-guide

A cryptographic hash function maps data to a fixed-size string of bytes. It has three core properties:

  1. Deterministic: Same input always produces the same hash
  2. Preimage resistance: Cannot reverse the hash to find the input
  3. Collision resistance: Cannot find two different inputs with the same hash

How Hashes Are Used

  • File integrity: Download a file and verify its SHA-256 checksum matches the publisher's
  • Password storage: Store hash(password + salt) instead of plaintext passwords
  • Digital signatures: Sign a hash of a document instead of the full document
  • Blockchain: Each block contains the hash of the previous block
  • Deduplication: Identify duplicate files by hash

Try computing hashes yourself with our free hash generator.