Sovrency is a self-custody hardware wallet from CrossBar, paired with a mobile application. It uses a 2-of-3 MPC design. One key share lives on the user’s phone, one in the hardware wallet, and a third is held for recovery only and takes no part in day-to-day signing. Every transaction needs the phone and the hardware wallet together, so no single device can move funds on its own. The wallet produces a standard Ethereum address and works with Ethereum and EVM-compatible networks.
The problem
On Ethereum, every transaction requires a network fee paid in ETH. For stablecoin users this is a persistent obstacle: a wallet can hold USDT and still be unable to send it without first acquiring ETH. USDT on Ethereum does not support the signature-based approval standards that other tokens use to work around this, so the problem cannot be solved at the token level.
What we built
Sovrency Wallet is adding gasless USDT transfers. A user can send USDT on Ethereum with zero ETH in the wallet. Sovrency’s sponsorship service covers the network fee, and a small service fee is settled in USDT instead.
From the user’s side:
- The fee is shown before confirmation and is capped at the maximum the user approves.
- The first gasless transfer asks for explicit approval on the hardware wallet to enable the feature. After that, each transfer needs a single confirmation.
- If sponsorship is unavailable, the wallet falls back to paying the network fee in ETH.
Nothing about the user’s address changes and no assets are moved to enable this.
How it works
The feature is built on Ethereum’s account abstraction standards. EIP-7702, activated with the Pectra upgrade, lets an existing wallet address delegate its execution to smart contract code, which is what allows a third party to sponsor its fees. ERC-4337 is the complementary standard that defines how such operations are packaged, validated and sponsored on-chain. Sovrency implements both, and because the MPC wallet is already a standard Ethereum address, users get the benefits without any migration.
Security is enforced at the signing step. Each transfer is signed as an EIP-712 typed-data message by the MPC key shares on the phone and the hardware wallet, with the decoded transaction details confirmed on the hardware wallet’s screen. The sponsorship service can only submit what the user has signed: it cannot alter the recipient or amount, and cannot move funds on its own. Every transfer carries a unique nonce and an expiry time to prevent replay.
Status
The full flow has been validated end to end on physical devices, covering the mobile application, the hardware wallet firmware and MPC signing. The ERC-4337 sponsorship infrastructure has been deployed to Ethereum mainnet and to several EVM Layer 2 networks, where it is undergoing further testing ahead of release. Ethereum will launch first, with Layer 2 support to follow.
References: EIP-7702 (https://eips.ethereum.org/EIPS/eip-7702), ERC-4337 (https://eips.ethereum.org/EIPS/eip-4337), EIP-712 (https://eips.ethereum.org/EIPS/eip-712).