What is HMAC? Signing webhooks, links and API calls
HMAC proves a message is unaltered and came from a key holder. How HMAC-SHA256 works, verifying Razorpay and Cashfree webhooks, signing video links, and mistakes to avoid.
Ideas & updates
The Upclass Blog
Security, piracy and engineering deep dives, plus practical ideas for growing your institute. From the team building Upclass.
More articles Page 7 of 11
Legal notice for copyright infringement: format and tips
When a legal notice works against resellers, ex-staff and notes sellers, what it must say, a sample structure for your lawyer, and next steps if it's ignored.
Django caching: per-view, fragment and low-level caching
Pick a Django cache backend, use cache_page, template fragment caching and the low-level API safely, and invalidate with signals and versioned keys.
Section 65B certificate (now BSA 63) for piracy evidence
Screenshots alone often fail as evidence. How to capture, hash and certify proof of a course leak under BSA Section 63, which replaced Section 65B in 2024.
Redis cache: how it works, and Redis vs Memcached
Why Redis is fast, how TTLs and eviction policies work, how to size memory, when persistence matters for a cache, and how Redis compares with Memcached.
Dynamic watermarking for video: why visible marks fall short
How pirates crop, blur, cover and compress visible watermarks in leaked lectures, why a visible mark alone isn't enough, and what to ask a vendor.
Caching strategies: cache-aside, write-through, write-back
Cache-aside, read-through, write-through and write-back compared: how each works, how each fails, and which suits course pages, progress and leaderboards.
How to protect PDF notes from copying: why locked PDFs leak
PDF passwords and copy locks don't stop leaks. How protected notes still get out through shared passwords, screenshots, photos and printouts.
Postgres materialized views: query-level caching
Precompute leaderboards and reports inside PostgreSQL: create and index materialized views, refresh them concurrently, schedule refreshes, and know the alternatives.
How to prevent screen recording on a website
Websites can't block or detect screen recording. How web lectures leak, why common web protections fall short, and what to ask your platform.
Cache invalidation and TTLs: strategies that work
TTLs, event-based deletes and versioned keys: choosing TTLs per data type, purging CDNs, avoiding stale reads after writes, and why eviction isn't invalidation.
Android FLAG_SECURE: what it blocks and what it can't stop
FLAG_SECURE keeps app screens out of screenshots and recordings, but not away from a second phone, rooted devices, emulators or audio capture.
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