The DeFi Mullet: Build with Stablecoins and Smart Accounts

How apps like Clave are using Smart Accounts, Stablecoins, and DeFi to build fintech onchain.

Introduction

Blockchain technology is eating finance. Stripe has announced Tempo, an EVM-compatible L1. Robinhood has announced an Ethereum L2 for tokenized stocks. The NASDAQ has announced future support for tokenized equity and 24/7 markets via blockchain technology. U.S. Congress passed the GENIUS Act, legitimizing the role of stablecoins in the financial system. And institutional adoption of Bitcoin and Ether has arrived.

Blockchain technology, and more specifically stablecoins, provides a foundational layer for a new financial system. A system that is borderless, transparent, and operates at a fraction of the cost of legacy finance. To fully unlock this potential, we need a bridge—a way to connect the powerful, decentralized rails of blockchain with the familiar, intuitive user experiences people expect.

This case study demonstrates how Rhinestone and Safe can be combined to build a stablecoin fintech app with the complexities of blockchain technology fully abstracted from the user. The DeFi Mullet: Seamless Fintech UX in the front, with a powerful DeFi backend powered by smart accounts and stablecoins. The example product is Clave, a stablecoin wallet that provides a Revolut-like banking experience built on blockchain technology.

The Challenge: Bridging to A Mainstream Audience

Builders face a fundamental trade-off: do they prioritize security and control, or user experience and accessibility? The traditional model forces a choice, creating a chasm between secure, but complex, on-chain solutions and user-friendly, but centralized, alternatives. The challenge was to create a product that is both:

• Secure and Self-custodial
• Intuitive and Accessible

The Solution: The DeFi Mullet

The combination of Rhinestone and Safe is the perfect embodiment of the DeFi Mullet philosophy.

The Front: The Smart Wallet

Safe smart account provides the foundation to build a polished, user-centric interface. 

• Passkeys for seamless user onboarding: Create a completely self-custodial, but seedphrase-less, user onboarding experience with zero reliance on a third-party service for storing and managing precious user key material. It’s all handled locally on the user’s device via a secure enclave.  
• Account recovery made simple: But what if the user’s device is lost, and with it, their keys. Unlike EOAs, smart accounts allow for key rotation, giving developers (and users) the flexibility to install third-party services (such as Lit Protocol, Magic Labs, or Turnkey) that can verify the user credentials (e.g., email or social login) before authorizing key rotation.
• Smart Sessions for single click UX: Users just want to click buttons. They dont want to create a cryptographic signature (i.e., FaceID scan) for every action within their wallet. This is where session keys shine. They allow users to pre-authorise actions for a given time, spending limit, or restricted set of functions. This approval only needs to happen once when opening the wallet, allowing interactions within the session to be as seamless as possible. 

Clave is a perfect example of these primitives at work. Paskeys for a clean login and transaction signing experience and Privy for account recovery. No seedphrase. No EOA guardians. Self-custody that is so easy your grandma could set it up.

The Back: Intent-Based Stablecoins and DeFi

Behind a simple interface powered by Safe smart account is the DeFi mullet, powered by Rhinestone intents, stablecoin, and DeFi. 

• Make crypto invisible with Rhinestone intents: Intents allow sophisticated entities, called solvers or relayers, act on the users behalf. This includes paying gas fees for users, supplying tokens on chains a user does not have funds, and finding the best onchain route for the users desired onchain outcome, such as swaps a stablecoin for another ERC-20. This eliminates chains, bridging, and gas fees for the user. 
• Ground your product in digital dollars, not tokens: Stablecoins are a familiar concept for any fintech user – digital dollars. With Rhinestone intents, all onchain operations can be denominated in stablecoins – gas, fees, and any DeFi operations. With digital dollars comes all the upsides of stablecoins – instant payment rails with no borders.
• Generate savings rates through platforms like Morpho: Ethereum DeFi creates saving rate opportunities that are both (debatably) lower risk and higher return than tradfi banks. USD stables currently offer a minimum of 5% on low risk opportunities, with battle tested alternatives as high as 9%. These APY opportunities are borderless and freely accessible with no prohibitive cost barriers.

With Rhinestone, Clave completely eliminates chains, bridging and gas. The application is a digital dollar-denominated (USDC) wallet with best-in-class Earn and Trade products that are void of blockchain complexity but capturing all the upside.

Implementation: From Problem to Production

Using the Rhinestone SDK, developers are able to deploy and manage Safe smart wallets and eliminate chains, bridging and gas fees through one simple API for intent-based transactions. We abstract away the complexities of wallet management with the required features for transaction signing, recovery, and more, whilst also bringing the stablecoin liquidity layer for seamless crosschain transactions. 

Get started with Rhinestone and Safe today by creating an API key today using the Rhinestone Dashboard and exploring our quickstart guide. To configure the underlying account as a Safe account, follow these simple steps.

Outcomes and Impact

By building with Rhinestone and Safe, developers can achieve several critical outcomes:

• Bridged the User Gap: Build a wallet offering that appeals to both crypto-native users and those that are new to the space without an understanding of seedphrases and gas.
• Demonstrated Scalability: The modular nature of the Safe smart account and Rhinestone shows how to build a flexible, scalable product that can adapt to new use cases, blockchains and DeFi protocols.
• Set a New Standard: This project serves as a template for other teams looking to combine the best of Web2-like UX and Web3, proving that security and usability are not mutually exclusive.

Conclusion: A More Stable Future

Stablecoins is disrupting traditional finance with instant, borderless, and cheap money rails that are digitally native. DeFi provides low risk saving rates far above traditional banking and a wider spectrum of assets are quickly coming onchain. Rhinestone and Safe provide the bridge between these emerging primitives and a mainstream audience that does not need or want to understand the intricate details of blockchain technology. 

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