Hash Generator

Cryptographic Hash Functions and Data Integrity

A cryptographic hash maps input of any length to a fixed-length digest. Three properties make it useful: the same input always produces the same output, a single changed bit produces a completely different digest, and the function cannot practically be reversed. That makes hashes ideal for verifying that a file, message or database row has not been altered in transit or at rest.

Not all algorithms age equally. MD5 (128-bit) and SHA-1 (160-bit) are both broken for collision resistance — researchers can construct two different inputs with the same digest — so they must never be used for signatures, certificates or anything security-critical. They remain acceptable as fast non-adversarial checksums, such as detecting accidental file corruption or deduplicating cache keys. SHA-256 and SHA-512, from the SHA-2 family, have no practical attacks and are the sensible default today.

One critical caveat: plain hashing is the wrong tool for storing passwords. General-purpose hashes are designed to be fast, which is exactly what an attacker with a GPU wants. Use a purpose-built password hash such as bcrypt, scrypt or Argon2 with a unique per-user salt and a deliberately high work factor. For verifying message authenticity between two parties, use HMAC with a shared secret rather than hashing the concatenated secret and message yourself.

Frequently asked questions