🔐 Privyra · SecureTalks

Private conversations, made simple. A privacy-first E2EE web messenger prototype (repo SecureTalks) with server-blind encrypted storage, identity verification, encrypted attachments, disappearing messages, and opt-in AI tools.

_{Solo maintainer · research & architecture · @kulharshit21}

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Snapshot

Privyra / SecureTalks is a privacy-first encrypted messaging prototype: plaintext stays in an unlocked browser session; Supabase holds ciphertext, AEAD metadata, and encrypted Storage blobs. Attachments (encrypt-then-upload) use the private encrypted-attachments bucket for direct chats — group attach remains incomplete in UI. Disappearing messages combine expires_at, RLS, purge_expired_messages(), and cleanup_expired_messages(). Group chat is a small-team MVP (symmetric epochs — not MLS). Opt-in AI runs only via mistral-ai-assist Edge Function (Next proxy disabled by default); normal send/decrypt never calls AI.

Docs: SECURITY_CLAIMS.md · LIMITATIONS.md · DEPLOYMENT.md · DEMO_SCRIPT.md · docs/THREAT_MODEL.md · docs/SECURITY_MODEL.md · docs/PRODUCTION_ENV_CHECKLIST.md · docs/CRON_CLEANUP.md · docs/privyra-graph-summary.json (curated agent / architecture graph)

⚠️ Timers and server deletion do not stop screenshots, malware, or a compromised device. This project does not claim to be “more secure than WhatsApp” without an independent audit — see LIMITATIONS.md.

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Repository on GitHub

Remote: kulharshit21/SecureTalks — description, topics (e.g. privyra, e2ee, supabase, libsodium), and releases are set there.

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Architecture

flowchart TB
  subgraph Browser["🔒 Trust boundary — your tab"]
    direction TB
    UI["Next.js App Router UI<br/>shadcn · Tailwind"]
    Vault["Device gate · PIN unlock<br/>private keys in IndexedDB (idb)"]
    Cipher["SessionCipher<br/>X25519 triple DH · XChaCha AEAD envelope"]
    FileAEAD["File symmetric AEAD<br/>random file key · nonce ‖ ciphertext"]
    UI --> Vault
    Vault --> Cipher
    Cipher --> FileAEAD
  end

  subgraph Edge["Supabase — hostile infra assumed"]
    direction TB
    Auth["GoTrue Auth"]
    PG["Postgres + RLS<br/>messages · members · attachments meta"]
    ST["Private bucket<br/>attachments (ciphertext only)"]
    RT["Realtime<br/>typing · inserts"]
  end

  Browser -->|"JWT"| Auth
  Cipher -->|"insert ciphertext row"| PG
  FileAEAD -->|"XHR upload ciphertext"| ST
  PG <-->|"membership-scoped SELECT"| Browser
  ST <-->|"policy via attachments row"| Browser
  PG --> RT

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Encrypt path (high level)

sequenceDiagram
  participant U as User
  participant C as Client crypto
  participant DB as Postgres messages
  participant S as Storage bucket

  U->>C: Plaintext / file bytes
  C->>C: derive outbound DH secrets<br/>wrap UTF8 manifest OR body in AEAD
  C->>DB: ciphertext + nonce + algorithm<br/>associated_data JSON (devices + conversation + ts)
  opt Attachment
    C->>C: random fileKey · AEAD(file)<br/>wrap fileKey with SessionCipher
    C->>S: POST ciphertext blob only
    C->>DB: attachments row (wrapped key + path + mime hint)
  end

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Threat model (honest)

Surface	What the server sees	What it never sees
messages	Ciphertext, nonce, protocol id, bound metadata JSON	Plaintext bodies
attachments	Storage path, wrapped file key blob (still ciphertext to infra without device secrets), MIME hint	Plain files
Client compromise	N/A — attacker reads decrypted UX same as user	—

Read docs/SECURITY_RLS_CHECKLIST.md after migrating. SECURITY_CLAIMS.md records what we do and do not promise.

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Stack

Layer	Choices
App	Next.js 16 · React 19 · Tailwind 4 · shadcn/ui patterns · lucide-react
Auth	Supabase Auth (+ SSR @supabase/ssr)
Crypto	libsodium-wrappers · session envelope + separate file AEAD domain
Data	Postgres RLS · Storage policies · optional pg cron purge

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Quick start

git clone https://github.com/kulharshit21/SecureTalks.git
cd SecureTalks
npm ci
cp .env.example .env.local   # fill NEXT_PUBLIC_SUPABASE_* + redirect URLs
npm run dev

Apply SQL from supabase/migrations/ via Supabase CLI or SQL editor (order matters).

Scripts

Command	Purpose
npm run dev	Local Next dev server
npm run build	Production build
npm run lint	ESLint
npm run typecheck	tsc --noEmit
npm run test	Vitest unit/crypto tests
npm run test:e2e	Playwright (configure env first)
npm run security:edge-health	Probe Edge Functions (cleanup + AI); needs .env.local with anon URL/key
npm run smoke:two-user-chat	Optional multi-user smoke script (configure test accounts first)

Auth / device recovery (UI): /forgot-password, /reset-password, /recover-device, /settings/security — see docs/SECURITY_MODEL.md.

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Scheduled expiry cleanup

After migrations, public.purge_expired_messages() deletes expired attachment objects then rows. Schedule with Supabase pg_cron or a trusted worker using service_role (already granted EXECUTE in migration). Never ship the service role key to the browser.

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Maintainer

Author & sole contributor: kulharshit21

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_{Built with intent · vibe-coded UI · honest crypto boundaries}