Hashing

Hashing is a one-way function that converts data into a fixed-length string, used for password storage and data integrity.

What is Hashing?

Hashing applies a mathematical function to convert input data into a fixed-size output (hash or digest). It's one-way—you cannot recover the original data from the hash.

Hash Properties

Deterministic: Same input always produces same output
Fixed Output: Any input produces fixed-length hash
One-Way: Cannot reverse the hash
Collision Resistant: Hard to find two inputs with same hash

Common Hash Algorithms

MD5: 128-bit, broken (don't use)
SHA-1: 160-bit, weak (avoid)
SHA-256: 256-bit, general purpose
SHA-3: Modern alternative
bcrypt/Argon2: For passwords

Common Misconceptions

"MD5 is still secure" - Broken, don't use
"Hashing and encryption are the same" - Fundamentally different
"SHA-256 is good for passwords" - Use bcrypt/Argon2 instead