Off-Pay

Final Workflow for OffPay with Offline-Only Transaction Validation

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1. QR Code for Bluetooth Pairing and Transaction Initialization

• Device B (Payee) generates a QR Code containing:
  • Payee account details (wallet ID or bank info).
  • Payee public key for encryption.
  • Bluetooth pairing credentials.
• Device A (Payer) scans the QR code to:
  • Establish a secure Bluetooth connection with Device B.
  • Retrieve the payee’s account information and public key.

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2. Bluetooth Pairing and Secure Channel Establishment

• After scanning, Device A and Device B are paired via Bluetooth.
• A secure communication channel is established using encryption (e.g., AES or ECDH) over the Bluetooth connection.

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3. Transaction Data Exchange

• Device A (Payer) enters the payment amount in the app.

• The app on Device A:

  • Encrypts the transaction data (amount, payer details, and transaction ID) with Device B’s public key.
  • Sends the encrypted transaction data to Device B over the Bluetooth connection.

• Device B (Payee):

  • Decrypts the received transaction data using its private key.
  • Verifies the transaction details, including the payer identity and amount.

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4. Local Transaction Validation (Fully Offline)

• The validation process happens offline:
  • Device A verifies that it has sufficient funds for the payment.
  • Device B checks the integrity of the transaction and confirms receipt.
  • A mutual digital signature process is initiated:
    • Device A signs the transaction with its private key.
    • Device B countersigns it with its private key, confirming the transaction.

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5. Offline Storage of Transaction Data

• After successful validation:
  • Device A stores the signed transaction details locally.
  • Device B stores the transaction receipt (confirmation details) locally.

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6. Syncing to Backend and Bank (When Either Device Comes Online)

• The transaction is fully validated and completed offline. However, syncing ensures that the transaction is recorded in the backend and bank systems.
• When either device comes online:
  1. The device uploads its locally stored transaction data (encrypted and signed).
  2. The backend validates the digital signatures and updates the payment records.
  3. The backend notifies the bank system to update the account balances.
  4. A transaction status confirmation is sent back to both devices (if both are online).

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Key Features of the Workflow

1. Offline Completion of Transaction:

   • All validation (payer funds, payee receipt) happens locally and offline.
   • The transaction is considered complete when both devices have signed the data and stored it.

2. Syncing for Record-Keeping:

   • The syncing step is optional for the transaction to work but is crucial for reflecting payment records in the bank system or backend database.

3. Security Through Cryptography:

   • Transaction details are encrypted, ensuring secure offline communication.
   • Digital signatures ensure authenticity and prevent tampering.

4. Bluetooth as the Only Dependency:

   • The entire transaction is facilitated by QR-based Bluetooth pairing, avoiding any reliance on the internet for validation.

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Example Scenario

Transaction Flow:

1. Device B (Payee) generates a QR code and displays it.
2. Device A (Payer) scans the QR code, pairs via Bluetooth, and initiates a transaction of $100.
3. Over Bluetooth:
   • Device A sends encrypted payment details to Device B.
   • Device B validates the details, countersigns, and confirms the transaction.
4. Both devices store the signed transaction data locally.

Syncing to Backend (Optional Until Online):

• If Device A comes online first:
  • It syncs the transaction details to the backend, which updates the bank records.
  • Device B receives a sync update when it later comes online.
• If Device B comes online first:
  • It uploads the transaction receipt to the backend, triggering bank updates.
  • Device A gets the sync update when it comes online.

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Advantages of This Workflow

• Full Offline Capability: The system doesn’t require internet connectivity to complete payments.
• Minimal Delay: Syncing only ensures backend and bank records are updated but doesn’t block the transaction.
• Security: Encryption and digital signatures protect transaction integrity and user data.
• Simplicity for Users: Scanning a QR code and relying on Bluetooth ensures a seamless experience.