Keshav
Work · Independent

DHVVS

Replaces paper health-visit logs with a proof chain — physical presence, on-device signing, async fraud scoring and a hash anchored on an EVM L2.

My part
Author
State
Prototype

What it does

Community health workers report visits on paper or simple apps, which invites ghost visits — and ordinary databases allow retroactive edits. DHVVS makes each visit a chain of evidence.

  1. 01NFC / encrypted QR + geofence
  2. 02ECDSA sign on device
  3. 03NestJS ingestion
  4. 04BullMQ
  5. 05Fraud scoring · L2 anchor
  6. 06Patient OTP confirm

Decisions

  • Sign before the network. The backend verifies a claim instead of creating one.
  • Keep the slow parts async. Fraud scoring (impossible travel, overlapping windows, stationary GPS clusters) and anchoring are queued, off the ingestion path.
  • Anchor a hash, not the record. The chain gets a hash of the verified visit; the relational record stays in Postgres.

Four apps in a Turborepo: an offline-first Expo mobile app, the NestJS backend, an admin dashboard with geospatial heatmaps, and a minimal patient portal.