Time Locked PDF

Identified the need for time-restricted document access — exam papers, timed assignments, and scheduled content releases that shouldn't be reachable outside a specific window.

Designed the access flow: server-side time verification to defeat client-clock manipulation, signed URLs for document access, and automatic expiration.

Built Vercel serverless functions for time validation, PDF serving with signed URLs, and access logging. All time checks happen server-side.

Built a clean UI showing countdown timers, access windows, and document availability with clear locked/unlocked indicators.

Embedded an in-browser PDF viewer that blocks direct downloads during restricted periods and watermarks authorised views.

Addressed timezone differences, daylight saving transitions, and concurrent access scenarios. Added graceful degradation for slow connections.

Server-side validation against URL manipulation and replay attacks, with rate limiting on access attempts.

Tested across timezones, browsers, and devices. Simulated clock manipulation attempts to confirm the server-side enforcement holds.

Applied final constraints — HTTPS enforcement, CORS policies, content security headers — and deployed to Vercel.

Added an access analytics dashboard, refined the UI from user feedback, and documented the security architecture for future maintainers.