Hashing

• Take any-length input and convert it to a fixed length hash output (128bit, 160bit, etc)
• Hash function always generate same hash for same input (idempotent)
• The hash function is ONE WAY
• Different input generate completely different hashes
• It's a one-way function. You cannot take the input value from the hash
• The input can be anything from a short string to a gigabyte file
• The hash verifies if the data was not changed! (Integrity)
• Keys in hashing are optional