Hash Generator

What a hash is for

A hash turns any input into a fixed length string, and the same input always produces the same result. Change a single character and the output is completely different. That property makes hashes useful for one thing above all: checking that data has not changed. Download a file, hash it, compare it against the hash the publisher listed, and a match tells you the file arrived intact and untampered with.

Hashing is not encryption

This confusion causes real problems, so it is worth stating plainly. Encryption is reversible with the right key, which is the entire point. Hashing is one way and there is no key that recovers the original, by design. So a hash is not a way to store something you need to read back later. If you need to protect data and retrieve it, you need encryption, not a hash.

Choosing an algorithm, and one important warning

• SHA-256 is the sensible default for file integrity and general use.
• SHA-512 produces a longer digest and suits the same purposes.
• SHA-1 and MD5 are broken for security. Treat them as checksums for accidental corruption only, never for anything a person might attack.
• Never use a plain hash to store passwords. Password storage needs a purpose built algorithm such as bcrypt or Argon2, which are deliberately slow and salted.