Hashing

What is Hashing?

Hashing is a one-way cryptographic function that transforms input data of any size into a fixed-size string, called a hash or digest. Unlike encryption, hashing is irreversible - you cannot retrieve the original data from the hash value.

Key Properties

• Deterministic – Same input always produces the same output
• Irreversible – Cannot derive original data from the hash
• Collision-resistant – Extremely difficult to find two inputs that produce the same hash
• Avalanche Effect – Small changes in input produce completely different outputs

Common Hash Functions

• SHA-256 – Widely used, 256-bit output
• SHA-3 – Latest SHA standard, more secure
• BLAKE2 – Fast and secure alternative
• bcrypt – Specifically designed for password hashing
• Argon2 – Winner of password hashing competition

Applications

• Password Storage – Store hashed passwords, not plaintext
• Data Integrity – Verify files haven't been tampered with
• Digital Signatures – Part of the signing process
• Blockchain – Used in cryptocurrency and distributed ledgers

Best Practices

• Use strong, modern algorithms (SHA-256, SHA-3, BLAKE2)
• Always salt passwords before hashing
• Avoid deprecated algorithms (MD5, SHA-1)
• Don't use hashing for encryption - it's not reversible
• Use specialized functions like bcrypt for password hashing