Security & Cryptography
NexDrop is architected so that your sensitive files, videos, documents, and credentials never touch a cloud storage server. Here is how our cryptographic security layers operate.
1. WebRTC Transport Security (DTLS-SRTP)
All WebRTC communication uses mandatory Datagram Transport Layer Security (DTLS). DataChannels are encrypted end-to-end between the two browser endpoints. Even if network packets are inspected on transit, the payload cannot be decrypted without the ephemeral DTLS session keys negotiated directly between the peers.
2. Application-Layer E2EE (ECDH + AES-256-GCM)
On top of transport encryption, every device generates an ephemeral ECDH (P-256) key pair whose public key travels inside the QR pairing code. Both devices derive the same AES-256-GCM session key via HKDF-SHA256, and every file chunk is individually encrypted with a unique 96-bit IV before it ever touches the DataChannel. Keys are never hardcoded and exist only in memory.
3. Short Authentication String (SAS Verification)
Because pairing codes are exchanged by QR or copy/paste, they could in theory be tampered with. To catch this, both devices derive a 6-digit Short Authentication String (e.g., 482 913) from the actual ECDH shared secret via HKDF. If both screens show the same code, no one altered the handshake. Users confirm this in the Verify dialog.
4. Streaming SHA-256 Integrity Verification
During transmission, the sender and receiver compute SHA-256 hashes incrementally. Upon completion, hashes are matched to guarantee bit-for-bit payload integrity without corruptions or silent drops.
5. Zero Cloud File Persistence
NexDrop is a fully static PWA: no database, no file storage. One-scan pairing uses a lightweight ephemeral signaling service that relays only connection metadata (session id, single-use token, SDP, ICE) and expires each session within minutes; the manual QR/paste code path needs no signaling at all. File contents never touch any server — they travel only over the direct peer connection.