What is Cryptographic Hashing?
A hash function takes an input (or 'message') and returns a fixed-size string of bytes. The output is typically a "digest" that looks like a random string of numbers and letters. Hashing is a one-way function—it is mathematically unfeasible to revert the hash back into the original input.
Key Characteristics of Hashes
- Deterministic: The same input will always generate the exact same hash output.
- Avalanche Effect: Changing a single character in the input will completely change the entire output hash.
- Collision Resistant: It should be extraordinarily difficult to find two different inputs that produce the same output hash.
Algorithm Comparisons
- MD5: 128-bit hash. Extremely fast but considered cryptographically "broken" due to collision vulnerabilities. Used widely for simple file integrity checks (checksums) where malicious tampering isn't a threat.
- SHA-1: 160-bit hash. Also deprecated for cryptographic deployment (SSL certificates), but highly utilized in version control systems like Git to identify file blobs.
- SHA-256 & SHA-512: Part of the SHA-2 family designed by the NSA. These are the current industry minimum standards for hashing passwords, calculating cryptocurrency blocks, and issuing TLS web security certificates.