The EF Funds ScopeLift to Advance Stealth Address Standardization and Umbra v2
January 8, 2024 / Ben DiFrancesco
Umbra started as a project built by ScopeLift for ETHGlobal's HackMoney hackathon in May of 2020. HackMoney was one of the Ethereum community's first large virtual hackathons—a reality brought about by the unfolding covid-19 pandemic.
A year later, Umbra launched on Ethereum mainnet. In its firth month in production, just under $4,000 worth of assets were processed by Umbra. Since then, the protocol has rolled out on 4 additional EVM networks. Last month alone, over $22 million in assets flowed through the Umbra contracts across these networks, with the majority of this volume occurring on Layer 2 rollups. In total, Umbra has processed cumulative assets worth $300 million across hundreds of thousands of transactions. Over 75,000 unique addresses having registered to receive privacy preserving payments.
To our knowledge, this makes Umbra the most widely used implementation of stealth addresses on Ethereum, the EVM, or any cryptonetwork, period. ScopeLift is incredibly proud to have led the way in making stealth addresses more accessible and useable.
With all that said, we also realize there is much more that needs to be done before stealth addresses, and all privacy tools, reach their full potential in the crypto ecosystem. That's why we're excited to announce that ScopeLift has received a grant from the Ethereum Foundation to help push stealth addresses forward on the EVM.
The terms of the grant began in December of 2023. It will fund our work for six months. Along with other critical sources of funding—such as Gitcoin and Optimism RetroPGF—it allows us to level up stealth address adoption. In the remainder of this post we'll cover the objectives and milestones for this work, along with how you can follow along and contribute as well.
ScopeLift has three main areas of focus for our stealth address work over the next 6 months. Those are:
- Finalizing the Stealth Address ERCs
- Architecting, Designing and Prototyping of Umbra v2
- Continuing improvements and maintenance for Umbra v1
Let's unpack each of these objectives in turn.
Stealth Address ERCs
The top focus of the next six months will be pushing for the finalization of two ERCs to standardize stealth addresses on the EVM. They are:
- ERC-5564 — Stealth Addresses: Private, non-interactive transfers and interactions
- ERC-6538 — Stealth Meta-Address Registry: A registry to map addresses to stealth meta-addresses
Together, these two ERCs create a lightweight, flexible and powerful set of tools to allow developers to adopt stealth addresses. The ERCs are designed to be interoperable and completely permissionless.
We believe this point is absolutely crucial. To truly gain traction, we believe a stealth address protocol needs to be a public good—one that can be permissionlessly integrated into dapps, wallets, and other protocols; and one that can't be turned off or censored by any organization or authority.
It's important to note that while ScopeLift has been contributing to these ERCs since the beginning, we're by no means the only entity in the ecosystem that has been contributing to them. In particular, we need to thank Matt Solomon (formerly of ScopeLift), Toni Wahrstätter, and Vitalik Buterin for their enormous contributions to the effort to advance stealth address standardization.
Beginning Umbra v2
The aforementioned ERCs aspire to be minimal yet powerful. They aim to make the fewest assumptions needed about how stealth addresses will be used by developers building on top of them. The core goal is to ensure dapps, wallets, and other protocols building on them are interoperable.
Once this critical task of establishing a permissionless standard is in place, we hope to see many developers building all kinds of interesting things on top. Our hope is to facilitate that experimentation, but also to participate in it ourselves. Umbra v2 will be an opinionated protocol built on top of the ERCs.
We already have some ideas of what Umbra v2 might look like—the features and capabilities it will include—based on three years of maintaining Umbra v1 in production. But there is still much we need to consider before embarking on a full blown implementation. Over the next six months, then, in parallel with our work on the standardization effort, we'll begin formally exploring the architecture and design of Umbra's second iteration. With any luck, we'll also be able to move into prototyping and even implementation during this time as well.
We intend to do as much of this work in public as possible. Keep an eye out for future posts.
Maintaining Umbra v1
While we're excited about the stealth address ERCs, and the second version of Umbra which they will enable, we're not abandoning Umbra v1. As noted earlier, Umbra v1 is—as far as we know—the most widely used implementation of stealth addresses in the entire cryptocurrency ecosystem. Thousands of users rely on the protocol each month, and with the next version of Umbra still many months away, we are committed to spending time adding features, improving performance, and generally keeping Umbra v1 in good health.
Not only is keeping Umbra v1 well maintained the right thing to do for our users, it's also the right thing to do for the future of stealth addresses. We've learned an enormous amount by building and maintaining Umbra v1, and we fully intend to continue learning and iterating while building out the standards and the next version. Stay tuned for lots of updates to Umbra v1.
The work described in this post has been underway at ScopeLift since early December 2023. Here are some of the milestones you can look out for as we continue our efforts in the first half of 2024:
|Release candidate ERC contracts ready for public review and scrutiny
|Alpha release of the TypeScript SDK
|ERC contracts audited by Trail of Bits
|ERC contracts deployed to testnet(s)
|Initial Umbra v2 plans published
|Beta TypeScript SDK released
|Final contracts deployed on major EVM networks
|Version 1.0.0 of the TypeScript SDK is published
|Preliminary Umbra v2 architecture docs, diagrams, prototypes, and mockups are published
Resources & Contributions
ScopeLift is excited to be funded to lead the way in stealth address standardization on the EVM. We are grateful to the Ethereum Foundation for providing this grant, and to other projects funding public goods like this—especially Gitcoin & Optimism (via RetroPGF).
While ScopeLift is proud to lead the way, a standardization effort is, by definition, a community act. We want to reiterate our thanks to those who have already contributed, especially Matt Solomon, Toni Wahrstätter and Vitalik Buterin. We also want to encourage those who are interested to get involved. To get involved, consider doing any or all of the following:
- Joining the stealth address standardization working group Telegram channel
- Checking out Toni's interactive site introducing ERC-5564
- Read Vitalik's Incomplete Guide to Stealth Addresses
- Reviewing ERC-5564 and ERC-6538, and submitting a PR in the public ERC repo if you see an issue
- Joining in on conversation on ETHMagicians forum
- Reviewing the in-progress ERC smart contract implementations