A continuously evolving collection of security-focused Java and Python code snippets demonstrating common authentication vulnerabilities alongside their secure, industry-aligned alternatives.
This repository is intentionally snippet-based — each file focuses on one specific security concept, making it easy to understand, reason about, and explain during technical interviews or security discussions.
This repository is maintained as a learning and reference workspace for authentication and security fundamentals.
It is designed for:
- 💡 Practicing secure coding principles
- 🎯 Preparing for technical and security-focused interviews
- 🛡️ Developing a security-first mindset as a software engineer
Rather than building a single large system, the focus is on small, isolated, realistic scenarios that mirror how authentication flaws and fixes appear in real-world codebases.
This repository is actively maintained and expanded incrementally.
- Currently contains 30+ focused Java and Python snippets
- New files added to cover advanced and edge-case auth scenarios
- Each update targets one authentication or security concept
- Changes are made through small, concept-driven commits
- Emphasis is on clarity, consistency, and defensive thinking
This update expands the repository beyond basic auth examples into realistic attacker-aware patterns commonly discussed in interviews.
- Plaintext password storage vulnerabilities
- Secure password hashing and salting
- Password strength validation and reuse prevention
- Insecure vs secure login implementations
- Hardcoded credentials vs environment-based secrets
- Timing attacks and constant-time comparisons
- Username enumeration vulnerabilities
- Brute-force attempts and account lockout logic
- Input validation vs sanitization pitfalls
- Weak randomness vs cryptographically secure randomness
- Session tokens, OTPs, and reset-token patterns
- Cookie security flags and CSRF basics
- Replay attacks and nonce usage
- Common string comparison mistakes in auth logic
- Basic audit logging and rate-limiting concepts
Each concept is demonstrated using minimal, framework-free code to keep the focus on core security reasoning.
- Each file is independent and can be run on its own
- Java and Python examples are intentionally minimal
- Code is meant to be read, executed, and explained, not copied blindly
- Ideal for quick revision, interview prep, or security walkthroughs
- Passwords should never be stored or compared in plaintext
- Secrets must not be hardcoded in source code
- Strong hashing with proper salting is essential
- Authentication logic should avoid information leakage
- Constant-time comparisons reduce timing-based attacks
- Security is about eliminating entire attack classes, not fixing symptoms
All code in this repository is provided for educational purposes only.
The snippets are intentionally minimal and not production-ready authentication systems. Their goal is to illustrate concepts, encourage defensive thinking, and support interview discussions — not to be used as drop-in solutions.
- Focuses on security fundamentals, not frameworks
- Uses small, explainable examples
- Demonstrates attacker-aware and defensive thinking
- Reflects incremental, real-world learning
- Actively maintained with intentional updates