Don't Leave Digital Footprints
with Sandcat

Sand Cat is a privacy-first, open-source application that enables quantum-secure, peer-to-peer Bitcoin transactions using encrypted QR codes — with or without an internet connection.

Built from the belief that financial privacy is essential to human freedom, Sand Cat ensures individuals can request or send Bitcoin securely, without exposing wallet addresses, personal metadata, or relying on centralized infrastructure.

In a time where AI is improving surveillance and government overreach is threatening financial sovereignty, Sand Cat offers the digital equivalent of handing someone physical cash — only faster, borderless, and quantum-resistant.

Why Sand Cat Exists

Today, even non-KYC Bitcoin users face real-world risks:

  • Reused addresses expose total wallet balances

  • QR code scanners leak payment info

  • Messaging platforms store and correlate transaction data

  • Blockchain analysis firms map entire social graphs of Bitcoin activity

Sand Cat prevents all of that by combining end-to-end encrypted communication with quantum-safe cryptography and offline QR code transmission.

It’s not just a messaging app. It’s a freedom tool.

Sand Cat App

How Sand Cat Works

Sand Cat uses two core technologies from the NIST post-quantum cryptography standardization process:

  • CRYSTALS-Kyber for key exchange (quantum-safe alternative to ECDH)

  • CRYSTALS-Dilithium for digital signatures (verifiable authentication)

Here's the simplified flow:

  1. A user creates a Bitcoin payment request, optionally including an amount and memo (following the BIP-21 standard)

  2. That request is encrypted with the recipient’s Kyber public key and digitally signed using the sender’s Dilithium private key

  3. The encrypted payload is encoded into a QR code

  4. The recipient scans and decrypts the QR to retrieve the request, verifying the sender’s signature in the process

This can all be done peer-to-peer — even offline — with no server, phone number, or account required.

Development Roadmap

Sand Cat will be developed in three phases:

  • Define mission, use case, and privacy principles
  • Choose tech stack (Python, Kyber, Dilithium, QR)
  • Secure domains: sandcat.app, sandcat.network
  • Set up core brand assets (logo, voice, tone)
  • Write public positioning content: What is Sand Cat / Why it matters

Goal: Build a minimal, local prototype demonstrating encrypted QR-based Bitcoin requests.

  • Generate and persist Kyber (key exchange) and Dilithium (signature) keypairs
  • Encode BIP-21 requests into encrypted messages
  • Sign messages with Dilithium
  • Output messages as QR codes
  • Scan QR code and decrypt payload on recipient side
  • Verify digital signature
  • Command-line interface or simple GUI
  • Unit tests for encryption/decryption flow
  • Save/load keypairs securely (local disk only)

Goal: Deliver a self-contained desktop app for private Bitcoin request messaging.

  • Package app with basic UI (Python/Tkinter or Tauri)
  • Address reuse protection (auto-generate fresh address per request)
  • Add memo + amount support (BIP-21 parsing)
  • Local key management (secure file storage + optional passphrase)
  • PSBT generation (optional) Downloadable builds for Windows, macOS, Linux
  • Open-source repo with install instructions

Goal: Build cross-platform mobile app with QR camera input/output.

  • Reimplement Kyber & Dilithium in mobile context (via liboqs or native bindings)
  • Support key generation, address request, QR encoding
  • Scan QR codes using native camera
  • Verify signature and show request details
  • PSBT or WalletConnect integration for “tap-to-pay” support
  • Wallet integration support (external broadcast)
  • Secure key storage using native mobile hardware (Secure Enclave / Android Keystore)

Goal: Add advanced privacy tools and make UX seamless.

  • Ephemeral keys and message expiry timers
  • Decoy QR codes or duress mode (e.g. fake amount or fake address)
  • Stealth address support (BIP-47 or future iteration)
  • Batch request / group QR generation
  • Encrypted QR file export (PDF or PNG)
  • Local PSBT signing + manual broadcasting
  • Multilingual interface

Goal: Allow optional online messaging over privacy-respecting relays.

  • Encrypted message transport over Tor or Nym
  • Onion-routed QR payload delivery (e.g. bridge for remote users)
  • Option for “delayed dropboxes” (encrypted dead drops)
  • Metadata obfuscation (timing randomization, cover traffic)

This stage is opt-in and disabled by default.

Goal: Let users transact with total independence from internet infrastructure.

  • Support scanning printed or screen-based QRs
  • Generate printable encrypted payment slips
  • Work across LAN (e.g. local mesh or direct Bluetooth)
  • Offline PSBT flow (sign on one device, broadcast elsewhere)
  • Optional SD card or USB transfer of encrypted requests

Goal: Enable integration, adoption, and independent deployment.

  • Full SDK for QR payload generation and decryption
  • Open QR standard format (Sand Cat Envelope Spec)
  • API for wallet integration (Sparrow, Specter, BlueWallet)
  • Verifiable message signing for multisig setups
  • App extension kits (command-line interface, hardware terminal integration)
  • GitHub repo with contributor documentation, tests, architecture diagrams

Goal: Prepare for long-term credibility, reproducibility, and secure usage.

  • Independent security review of core encryption flow
  • PQ signature verification test vectors
  • Deterministic builds / reproducible releases
  • Key backup and recovery UX
  • Transparent donation accounting (if applicable)
  • Binary signing + official public key

Goal: Reach those who need it. Build lasting infrastructure.

  • Launch on sandcat.app and sandcat.network
  • Publish whitepaper or technical overview
  • Launch GitHub org or Foundation structure
  • Add .onion and .ipfs mirrors
  • Community bug bounties
  • Forum, GitHub Discussions, or Signal group
  • Merchandise, FOSS grants, or donation matches to sustain dev

  • Integrate stealth protocols (e.g. ZK-SNARK proof-of-payment)
  • Add group mode with threshold keys
  • Build Sand Cat hardware tool (air-gapped QR signer)
  • Participate in PQ open-source crypto ecosystem
  • Enable global usage in restricted regimes, warzones, and economically censored regions

How to Support the Project

Sand Cat is a open source project funded by those who believe that privacy is not optional.

Contribute to Development

Visit our GitHub repository to view open issues, contribute code, or help with documentation and testing.

Donate with Bitcoin

100% of Bitcoin donations go toward development costs and contributor bounties. We never store your information, track donations, or publish addresses.

Donation Address: bc1qc9rrqy75sj8h83j3emcjq6vkehgsc8frcgrjy9

For multisig or larger support options, please contact the team directly.

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