Easily generate hash values like SHA-256/SHA-1/MD5 from text. Useful for password verification, file checking, and tamper detection.
Q1
A fixed-length value calculated from original data. Used for tamper detection, password storage, file verification, etc.
Q2
SHA-256 is safer and recommended. MD5 is fast but collisions have been found, making it unsuitable for important uses.
Q3
Basically irreversible. Be careful of brute force and dictionary attacks.