Emergency Cash

Emergency Cash / Emergency Digital Cash is an offline-first payment system built directly on the ARC blockchain, designed for emergency and disaster scenarios where internet access and traditional financial infrastructure are unreliable.

Physical NFC cards are turned into self-custodial crypto wallets. Each card deterministically derives an Ethereum-compatible address from its UID and is represented onchain as an ENS subname, giving every card a human-readable and verifiable identity.

Cards can hold USDC balances that are either funded directly or borrowed on ARC using onchain collateral. This allows credit-backed value to live on a physical card, enabling spending even when users do not pre-fund wallets. Payments can be authorized completely offline using cryptographic payment intents signed by the card wallet and later settled onchain when connectivity is restored.

ENS is used as a decentralized identity layer rather than just a naming system. Card ownership, metadata (UID, token, chain), and payment context are stored as ENS records, making payment flows transparent, inspectable, and composable. The system replaces physical cash in emergency kits with cryptographically trusted, ARC-native digital cash.

Design uses borrow/lend method to enable money to work more. Today's world, there are a lot of dependency on Internet. This could be harmful when there are extreme conditions or earthquakes. This system tried to exchange the good-old physical cash in emergency bags with crypto cards depending on the crypto-economic trust.

The system combines embedded hardware, cryptography, identity protocol and ARC-native DeFi infrastructure.

NFC cards are read using an STM32-based reader. Each UID is deterministically mapped to a private key using a secret-bound keccak derivation, producing stateless card wallets without secure elements. The same card always derives the same address, while keys are never stored on the device.

Onchain identity is managed using ENS NameWrapper. Each card receives an ENS subname, with resolver records storing the card’s address and structured metadata such as UID, token type, and chain. Optional reverse records allow addresses to resolve back to human-readable card names.

For liquidity, the system uses ARC’s lending infrastructure directly. ETH is supplied as collateral, and USDC is borrowed on ARC and transferred to the card wallet. ARC treasury contracts are also used for batch USDC payouts and settlement, demonstrating real financial flows on ARC rather than simulations.

Payments follow an offline-first design. The card wallet signs payment intents offline (EIP-191), which are later verified and settled onchain on ARC. This creates a hybrid model where authorization is offline but settlement is fully onchain. All components are open-source and connected via lightweight Node.js services using ethers.js.