Built a system that lets multiple organizations search each other's data without exposing sensitive content, using a federated RAG pipeline with FAISS, BM25, and cross-encoder reranking.
Implemented 4 privacy layers — embedding noise (Differential Privacy), score encryption (Homomorphic Encryption / CKKS), binary hashing (LSH), and secure aggregation — preserving 94% retrieval accuracy while fully hiding individual scores. Tested defenses against 4 real-world attacks (membership inference, score leakage, embedding reconstruction, query fingerprinting); all score-based attacks dropped to random-guess accuracy.