Hash functions are fundamental cryptographic tools that convert input data of any size into a fixed-size output called a hash or digest. They are deterministic, meaning the same input always produces the same output, and they are designed to be one-way functions—practically impossible to reverse.

Algorithm Differences

• MD5: 128-bit hash (32 hex characters). Once widely used but now considered cryptographically broken due to collision vulnerabilities. Still useful for non-security checksums.
• SHA-1: 160-bit hash (40 hex characters). Deprecated by NIST in 2011. Google demonstrated practical collisions in 2017. Avoid for security purposes.
• SHA-256: 256-bit hash (64 hex characters). Part of SHA-2 family. Currently considered secure and widely used in blockchain (Bitcoin), SSL/TLS certificates, and file integrity verification.
• SHA-512: 512-bit hash (128 hex characters). Even stronger than SHA-256, used in high-security applications.

Key Properties

• Avalanche Effect: A small change in input produces a drastically different hash output.
• Collision Resistance: It should be computationally infeasible to find two different inputs with the same hash output.
• Determinism: The same input always produces the same hash.

Use Cases

SHA-256 is the gold standard for modern applications: blockchain verification, password storage (with salting), SSL certificates, file integrity checksums, and digital signatures.