Nishchal Baghele on Instagram: "Ever wondered how Authenticator apps create 6-digit codes every 30 seconds — even offline? 🔐 • It’s not random, it’s TOTP (Time-based One-Time Password) — defined in RFC 6238 ⚙️ • When you scan that QR code, it stores a secret key shared with the server 🧩 • Your phone divides the current Unix time by 30 → gets a time window ⏱️ • Then it runs: HMAC_SHA1(secret, timeWindow) → produces a 20-byte hash 🔢 • Extracts 4 bytes using dynamic truncation, converts to a 31-