Notes on backend engineering and security research by Kartik Jain.https://jkartik.in/enhttps://jkartik.in/blog/zero-knowledge-sharing/https://jkartik.in/blog/zero-knowledge-sharing/How GhostShare shares notes and files in real time while making the server mathematically unable to read them — in-browser key derivation, AES-GCM, and direct-to-R2 encrypted uploads.Sat, 18 Jul 2026 00:00:00 GMTApplied cryptohttps://jkartik.in/blog/btree-storage-engine/https://jkartik.in/blog/btree-storage-engine/What actually happens between INSERT and the disk — building bad-db's on-disk format, a hand-rolled B-Tree index, tombstones, and compaction in plain Java.Thu, 16 Apr 2026 00:00:00 GMTSystemshttps://jkartik.in/blog/where-llm-guardrails-break/https://jkartik.in/blog/where-llm-guardrails-break/I built a prompt-injection contest and handed a few hundred people a scoreboard and a reason to break it. Here's what actually cracks an LLM's guardrails — and what it means for defending them.Fri, 03 Apr 2026 00:00:00 GMTSecurity