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Overview

On Ethereum there are two types of accounts: externally owned accounts (EOAs), and contracts accounts. The former type is the only one that can initiate transactions, while the latter is the only one that can implement arbitrary logic. This limitation prevents some interesting use cases, such as the ability to sign transactions via means that don't require the private key, transaction fees to be paid in tokens other than ETH, subscriptions, flash loans without deploying proxy contracts, and more.

Although not required to interact with Radian, some key features are only possible when using a a contract account. Radian provides a complete protocol for creating contract accounts (Hyper Wallets), as well as a protocol for new types of smart contracts to be created that take advantage of Hyper Wallets (Hyper Apps).

Certain protocol modules (such as the Paymaster) are themselves Hyper Apps. In the same way that you can install apps onto your smartphone, you can install Hyper Apps onto your Hyper Wallet.

Hyper Wallets and Hyper Apps are only available on the zkSync deployment of Radian, as it is made possible by zkSync's native account abstraction support.

Hyper Apps​

Hyper wallets expose a standard interface for interacting with Hyper Apps. Because Hyper Apps can request elevated permissions for Hyper Wallets, they must be explicitly installed. At a high-level, permissioning of Hyper Apps are represented as counterfactual delegations except unlike the Delegatable protocol, it does not require other contracts to inherit from another contract in order to be compatible -- it is natively compatible with all smart contracts by default.

Use cases​

Paymaster​

The Paymaster is a Hyper App that allows you to pay for gas fees in any ERC20 token. This means hyper wallets can participate, execute, and interact with any dApp or smart contract without having to hold ETH.

Subscriptions​

Although there has been attempts to create subscription protocols on Ethereum L1, they require the payment token to be wrapped, or in other cases require the user to lock up their tokens in a contract. This does not acctually solve the problem of subscriptions, as the user actually has to move the tokens out of their wallet ahead of time in one form or another, and is more akin to a one-sided escrow contract rather than a subscription. A hyper app can request a "pull" permission with some limit on the amount of tokens that can be pulled over some interval. With Hyper apps, real subscription services can be implemented.

Multi-Factor Authentication / Recovery​

Hyper Wallets authorize transactions using a dynamic signatured scheme. Hyper Wallets implemented a dynamic version of EIP-1271 where the implementation of the isValidSignature function is extended when A Hyper App is installed. This allows implementing multi-factor authentication, recovery schemes, "pulls" from other contracts, and more.

Flash Loans​

Some of the most powerful DeFi strategies involve flash loans. Flash loans are loans that are taken out and paid back in the same transaction. In order to verify that the loan is paid back, the last "execution" step of the transaction involves the contract giving out the flash loan to verify that it has been paid back. It is a vulnerability otherwise, since allowing execution afterwards can result in the contract giving out the load not being paid back. Therefore, flash loans typically require an onFlashLoan callback to be implemented by the contract that is borrowing the loan. This is not possible with EOAs, but is possible with Hyper Wallets. Hyper Apps can request permission to hook into this callback, allowing them to implement flash loans without deploying a proxy contract.

Attestations​

One of the experimental features of Radian is the uncollateralized lending protocol which can be used to as a buy-now-pay-later type of service. In traditional systems, the merchant pays a fee when receiving this type of payment to the lender. The merchant is incentivized to do this because it is possible that this a sale that would not have been made otherwise. However in the case of Radian, the merchant would instead pay in terms of risk.

To give a more technical description, the merchant receives the payment wrapped in a NFT that can only be unwrapped when the payer repays the protocol. This means that the merchant should only accept these payments from users that are likely to pay off their loan.

The immediate though you might have next is -- but this is the blockchain, how can we gauge this? The protocol itself provides the ability to query the interactions between the user and Radian, but this may not be enough.

Therefore, we envision that there will exist a class of Hyper Apps that users can install onto to their Hyper Wallet that attest to something about the user using a zero-knowledge proof.

For example, the CoinCircle Hyper App is an example of a hyper app that a user can install on their Hyper Wallet and link to their CoinCircle account, generating a proof that the user has a unique verified identity on the platform without revealing any information about their identity. This would require that the merchant trusts CoinCircle in order to trust the attestation.