Why TOTP 2FA Verification Fails in Production: 5 Cryptographic Edge Cases
Implementing Time-Based One-Time Passwords (TOTP, RFC 6238) seems straightforward: generate a 160-bit shared secret, render an otpauth:// QR code, and verify a 6-digit code against an HMAC-SHA1 digest. Yet, authentication services regularly encounter mysterious verification failures. A user enters the exact code shown on their screen, but the server rejects it. Here are 5 subtle edge cases in TOTP implementations and how to resolve them. TOTP secrets are encoded in Base32 (RFC 4648). However, st
🎯 Vulnerability: Web Security Vulnerability
💡 Defense Fix: Implement strict input validation, contextual output encoding, and enforce least-privilege authorization controls.