The Universal Ethereum Signer App Launches First on Passport

Developed by Ledger cofounder Nicolas Bacca, the app runs on KeyOS, Foundation's open source operating system that lets independent developers build apps for Passport.

Today, we're announcing the beta launch of the Universal Ethereum Signer on Passport Prime.

Developed by Ledger cofounder Nicolas Bacca, now CEO of ZKnox, with the work funded by an Ethereum Foundation grant to ZKnox, the app lets users review and sign Ethereum transactions and messages on dedicated open source hardware, keeping their private keys off their phone or computer.

Passport was chosen as the app's first hardware platform because developers can build on KeyOS without asking for our permission. Developers can write the software that runs on the device, design the screens users see, and release their own updates. Passport owners can then install these apps themselves, without waiting for us to add new capabilities through a system update.

Nicolas Bacca, Ledger cofounder, CEO of ZKnox, and developer of the Universal Ethereum Signer, explains why Passport was chosen:

“Having enough memory lets us reuse well-tested open source code instead of writing everything from scratch. On Passport, we can do that in an open development environment, with KeyOS keeping the signer separate from other apps on the device.”

Built for Independent Developers

We began building KeyOS in late 2022 so independent developers could create security apps without being given access to everything stored on the device.

The operating system gives each app its own protected environment, storage, and permissions; the Ethereum signer, for example, receives its own signing keys by default, separate from those used by other apps. This allows users to add Ethereum signing to the same device they use for Bitcoin, login credentials, and private files.

Our cofounder and CEO, Zach Herbert, explains the thinking behind KeyOS and why security hardware should evolve alongside its users:

“When you buy security hardware, you should be able to keep using it as your needs change. You shouldn't have to buy another device every time you want a new capability, or wait for the manufacturer to build it. We built KeyOS so developers can bring those ideas to users themselves.”

How the Universal Ethereum Signer Works

For Ethereum users, the app works alongside compatible wallets on their phone or computer. Wallets such as Rabby and MetaMask support the relevant QR signing standards, and both have been tested with the Universal Ethereum Signer by Nicolas Bacca on the Sepolia Ethereum test network.

After preparing a transaction in that wallet, users scan its QR code with Passport's camera and review the request on Passport's screen. If they approve it, Passport produces a digital signature and displays it as a QR code for the wallet to scan.

The signature returns to the wallet while the private keys stay on Passport, with no USB or Bluetooth connection needed for signing.

To help users check what they are signing, the app implements Verifiable Signing. Alongside the destination, amount, fees, and network, it displays a cryptographic fingerprint of additional transaction data that users can compare with an independently verified value before approving the transaction.

Expanding What's Possible on Passport Prime

The launch follows Legacy Mode, which brings existing open source apps developed for Ledger to Passport. With the Universal Ethereum Signer, users can now install an Ethereum app built directly for KeyOS.

“We're pleased to support ZKnox's work on the Universal Ethereum Signer, an open source app designed to run across multiple hardware platforms,” said Nicolas Consigny, member of the Ethereum Foundation’s Strategy Team. “The app launches first on KeyOS, with additional hardware integrations already in development.”

Availability and Getting Started

The Universal Ethereum Signer is available in beta today as an optional, manual installation on Passport Prime, with distribution through Foundation's app catalog planned for this winter.

Source code and installation documentation are available in the Ethereum GitHub organization.

Interested in building your own app for Passport Prime? Explore the tools and documentation on our developer portal.