Cryptography

3 articles

dsa8 min read

Euler's Totient Function Explained — Phi(n) Computation, Sieve Variant in O(N log log N) [Cryptography, Google]

Eulers totient function phi(n) counts integers up to n coprime to n and underpins RSA, modular inverse for composite moduli, and Eulers theorem. Master the prime-factorization formula, the sieve variant in O(N log log N), and the multiplicative-function tricks that make phi indispensable for competitive programming.

March 19, 2026Read →

dsa8 min read

Chinese Remainder Theorem (CRT): The Modular Arithmetic Superpower

Learn the Chinese Remainder Theorem from scratch. Understand the math, build CRT from extended GCD, handle non-coprime moduli, and ace cryptography and competitive programming interview questions.

March 19, 2026Read →

JWT7 min read

JWT Security Pitfalls — Algorithm Confusion, Key Rotation, and Token Theft Prevention

Prevent algorithm confusion attacks, implement safe key rotation, detect token theft with refresh token families, and secure JWTs with binding and revocation strategies.

March 15, 2026Read →