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BLE · Ed25519 · Zero Connectivity

zenpay.

Emergency offline payment network.
Peer-to-peer transfers over Bluetooth. No internet. No servers.

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BLE GATT Ed25519 Signing Zero Servers Offline Transfers Liquidity Reserve Cover Transitions Auto-Scale UI Persistent Identity 0dp Corners OTA Updates BLE GATT Ed25519 Signing Zero Servers Offline Transfers Liquidity Reserve Cover Transitions Auto-Scale UI Persistent Identity 0dp Corners OTA Updates
Jetpack Compose Google Tink GATT Server GATT Client OkHttp 4.12 SharedPreferences Instrument Sans Instrument Serif Shadcn Aesthetic Monochrome Jetpack Compose Google Tink GATT Server GATT Client OkHttp 4.12 SharedPreferences Instrument Sans Instrument Serif Shadcn Aesthetic Monochrome

The Protocol

01

Initialization

On first launch, the user establishes their identity. This generates a unique Ed25519 cryptographic keypair locally on the device.

02

The Vault

Devices are granted a random emergency balance (₹1,000 – ₹5,000). This balance is strictly local and hidden behind a square-edged PIN pad for privacy.

03

Discovery

Receivers act as "Terminals," broadcasting their identity via BLE Scan Response packets. Senders scan the local environment to detect active nodes in proximity.

04

Transaction

Senders select a node, enter an amount validated against their current balance, and authorize the transfer with a PIN.

05

Signing

Every transaction is cryptographically signed using the sender's private key. The receiver verifies this signature against the sender's public key before accepting funds.

06

Acknowledge

Upon a successful GATT write, the receiver's dashboard triggers a high-impact "You've Got Paid!" screen with full sender details and transaction hashes.

Zero-Connectivity Transfers

Pure BLE-based GATT communication. No Wi-Fi, no cellular, no external servers involved in the transaction pipeline.

End-to-End Signing

Ed25519 signatures ensure non-repudiation and prevent data tampering across every single transaction.

Cover Transitions

PowerPoint-style slide animations where new layers slide over old ones, ensuring a solid, heavy-duty feel.

Auto-Scaling UI

Payment displays dynamically adjust font size to handle large balances without layout overflow.

Persistent Identity

User profiles and cryptographic keys are saved securely, skipping onboarding after the first setup.

OTA Support

Integrated version checking via OkHttp to prompt users for updates when they regain internet access.

Technical Stack

Permissions

BLUETOOTH_SCAN
BLUETOOTH_ADVERTISE
BLUETOOTH_CONNECT
ACCESS_FINE_LOCATION

Crafted and secured by Fawaz.
zenpay is a custom-crafted financial utility focused on high-stakes reliability.

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