Beginner LevelWeb Security & Cyber Defense
What are Cryptographic Hash Functions (SHA-256) and their core properties (one-way, collision-resistant)?
❓ Interview Prompt: Explain Cryptographic Hash Functions, SHA-256, determinism, Avalanche Effect, One-Way property (pre-image resistance), and Collision Resistance.
A Cryptographic Hash Function is a mathematical algorithm that maps data of arbitrary size to a fixed-size bit string (e.g. SHA-256 produces a 256-bit / 64-hex-character output):
4 Essential Properties:
1
Deterministic: The same input always produces the exact same hash output.
2
One-Way (Pre-Image Resistance): Computationally infeasible to reverse a hash back to its original input.
3
Avalanche Effect: Changing a single input bit drastically changes the output hash.
4
Collision Resistance: Computationally infeasible to find two different inputs that produce the exact same output hash.
Code Implementation Example
typescript
import crypto from 'crypto';
// SHA-256 Hash Computation
const hash = crypto
.createHash('sha256')
.update('Hello World')
.digest('hex');
console.log(hash); // a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e💡Computing a SHA-256 cryptographic hash in Node.js.
🎯 Interview Key Takeaway
Cryptographic hash functions are deterministic, one-way, avalanche-sensitive, and collision-resistant.
#Cryptography#SHA-256#Hashing#Beginner
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