A Deep Dive into Hash Functions and Their Real-World Applications

When I first encountered hash functions in class, they seemed simple: take some input, run it through a function, and you get a fixed-length output. But the more I studied, the more I realized that hashing is a cornerstone of modern computing.

What is a Hash Function?

• Determinism: same input → same output.
• Efficiency: can process data quickly.
• Collision resistance: hard to find two different inputs with the same output.
• Pre-image resistance: infeasible to reconstruct input from output.

Applications in Technology

1. Databases and Indexing — Hash tables allow constant-time lookups.
2. Cybersecurity — File checksums (SHA-256) verify data integrity.
3. Password Storage — Passwords are stored as hashes, not plain text.
4. Blockchain — Bitcoin’s Proof-of-Work is built on SHA-256 hashing.

My Experiment

I implemented a custom C++ hash and compared it with std::hash and SHA-256. Results:

• Naïve function → many collisions on large datasets.
• std::hash → decent distribution, but not secure.
• SHA-256 → slower but essentially collision-free for my test size.

Future Exploration

• Benchmark cryptographic vs. non-cryptographic functions.
• Test larger datasets.
• Explore Merkle Trees (hash-based data verification).