SCF #42 | Build Track | Open Track
Zelf Legacy: Biometric Inheritance Infrastructure for Stellar
Requested Budget: $90,000 USD (in XLM)
Organization: Zelf World LLC (Wyoming, USA)
Executive Summary
Imagine creating multiple self-custody wallets—one for online trading, another for long-term investments, and a third for exploring DApps. Over time, their combined balance may grow to thousands or even tens of thousands of dollars. Yet you maintain peace of mind knowing that, in the event of a post-mortem or prolonged inactivity, your loved ones will still be able to access those funds.
Zelf Legacy enables you to manage inheritance without moving funds or relying on a central party. Instead of transferring assets, it transfers access rights to beneficiaries—activated only after they verify their identity through liveness detection and biometric proof. No private keys are exposed, no biometric data is stored, and no funds are lost due to missed transfers or fees.
We've already built the hard part. Our HumanAuthn technology (previously referred to as ZK Face Proofs) derives a private key from your face, enabling a self-custody wallet with no seed phrases and no servers. The result is a ~350-byte encrypted verifiable credential—visualized as a QR code—which we call the ZELF ID. Stellar is the right partner for an inheritance solution: identity, payments, rightful ownership, and ensuring assets reach family when you're gone. Our plan for the $90K funding is to build Soroban contracts, a heartbeat protocol, an oracle (currently at proof-of-concept stage), and the necessary tooling natively for Stellar—built from the ground up, not ported from another chain.
What Is Zelf?
Zelf is a cybersecurity solution built on a proprietary authentication and encryption primitive called HumanAuthn (previously referred to as ZK Face Proofs). Unlike traditional authentication methods, HumanAuthn anchors trust in live human presence rather than hardware verification, creating a device-agnostic, zero-template, biometric-bound identity layer. With a simple face scan, an ephemeral cryptographic key is regenerated to access your funds—eliminating the need for seed phrases or reliance on custodial servers and databases. Zelf is available on Web Extension, iOS, and Android.
What Is Zelf Legacy?
Zelf Legacy solves the most critical unaddressed problem in crypto: "What happens to your assets when you die?"
Most inheritance solutions lock funds inside smart contracts. Zelf Legacy takes a different approach. Instead of moving assets, it transfers access rights to beneficiaries—only after the owner's inactivity is verified and beneficiaries confirm their identity through face verification and ID. The assets remain safely in the original wallet the entire time.
How It Works
Step 1: Create Your Will
In the Zelf app, turn on Legacy Mode and pick your beneficiaries. Each one is bound via ZELF ID, with zero-template biometric storage. The result, each of the beneficiaries face, becomes the key to obtain access rights.
- Legal Smart Contract Wrapper on Soroban
- Biometric Beneficiary Designation via ZELF ID
- Policy encrypted and stored on IPFS & Arweave (immutable, decentralized)
- Shamir's Secret Sharing (SSS) splits the seed phrase into shares. You set the rules: consensus on 2 of 3 or 3 of 5, pick a lawyer or opt out, choose one beneficiary or several. Everything is configurable.
Step 2: Heartbeat Protocol
The Zelf app pings the Soroban contract periodically to prove the owner is still alive. The verifiable credential (QR code) that the owner must authenticate with is lightweight and private:
- Nobody can tell if you have a policy
- Heartbeats are signed; liveness detection blocks spoofs
- Owner sets the inactivity window (30 days to 24 months) and grace period
- Verifiable credential cuts on-chain storage by 100–1000x
Step 3: Secure Claim
Once the owner's inactivity and grace period are over, beneficiaries can claim. They must perform three checks:
- Face match: live scan against the ZELF ID the holder registered. No biometric data shared.
- Government Issued ID check: Verifik's KYC (190+ countries).
- ZK disclosure on Soroban: contract verifies entitlement and releases credentials. Keys stay off-chain.
Why We Don't Lock Your Funds
| Approach | Fund Transfer (typical approach) | Access Rights (Zelf Legacy) |
|---|---|---|
| User retains control | No. Funds locked in contract | Yes. Full control until inheritance |
| Smart contract risk | High. Funds at risk if contract is exploited | Minimal. Contract holds policies, not funds |
| DeFi composability | Broken. Locked funds can't be used | Preserved. Assets remain active |
| Yield/staking | Lost during lock period | Continues normally |
| Multi-chain assets | Requires per-chain deployment | Single policy covers cross-chain access |
| Legal enforceability | Uncertain. Code-is-law | Supported. Produces verifiable evidence for lawful off-chain execution |
Technical Architecture
HumanAuthn engine is already completed. Guardian Oracle is in proof of concept. We need to build the Soroban contracts, heartbeat protocol, oracle completion, and Stellar SDK layer.
Stellar Integration Plan
Stellar-Specific Building Blocks Used
- Soroban Smart Contracts (Rust): PolicyRegistry, Heartbeat accumulator, Claim verification logic. Directly Stellar-specific: replaces our Anchor/Solana program.
- Soroban Three-Tier Storage:
Persistentfor policy state and heartbeat root,Temporaryfor intermediate claim state,Instancefor contract configuration. No equivalent on other chains. - Soroban
require_auth()model: Replaces implicitmsg.sender. Explicit authorization required per Stellar's account model. - Soroban Event System: Heartbeat emissions use Soroban events rather than state writes, reducing per-heartbeat cost to near zero.
- BLS12-381 Native Curve Support: Soroban's built-in BLS12-381 support allows on-chain HumanAuthn verification without an external library. This is one of the primary technical reasons Stellar was chosen over EVM chains.
- Stellar Wallets Kit: Used in Tranche 3 SDK for Freighter/Lobstr wallet integration examples.
- IPFS + Arweave (storage layer): Policy metadata and ZELF ID packets stored off-chain; Stellar Ledger records only state hashes and events.
What We Already Have (Proven Components)
We're not starting from scratch. Most of the budget will be dedicated to building the components specifically required for Stellar.
| Component | Current Stack | Stellar Adaptation |
|---|---|---|
| HumanAuthn Engine | TypeScript/Native SDK (offline) | None needed. Chain-agnostic. |
| Inheritance business logic | Rust (Anchor/Solana) | Medium. Same language, swap macros and storage model. |
| Heartbeat Protocol | Solana + Light Protocol | Medium. Soroban events + BLS12-381 + Merkle accumulator. |
| Biometric SDKs | Web, iOS, Android | None needed. Client-side. |
| KYC/AML | Verifik Production API | None needed. Backend service. |
| Guardian Oracle | Proof of concept (Node.js) | Medium. Complete and adapt to Soroban. |
| Arweave/IPFS storage | Production integration | None needed. Chain-agnostic. |
Key Technical Differences: Soroban vs. Solana
| Aspect | Solana | Soroban |
|---|---|---|
| Language | Rust (Anchor) | Rust (Soroban SDK) |
| Auth Model | Implicit msg.sender | Explicit require_auth() |
| Storage | PDAs (accounts) | Typed storage (Persistent/Temporary/Instance) |
| H.A Support | Via Lit Protocol (external) | Native BLS12-381 curves |
| Tx Cost | ~$0.00025 | ~$0.0001 |
| Finality | ~400ms | ~5 seconds |
Stellar Integration Flow
Data flow showing exactly how Stellar components participate in the inheritance lifecycle:
Tranche 1: MVP ($25,000)
Timeline: 5 weeks
Soroban Inheritance Registry Contract + ZELF ID Integration. Build the Soroban contract that stores inheritance policy metadata and enforces claim eligibility. The contract integrates with ZELF ID for biometric verification. The Heartbeat Protocol integrated with Merkle proof-based for history verification. The result is a simulated end-to-end inheritance event on Stellar Testnet.
Architecture (5 weeks breakdown)
Tranche 2: Testnet ($35,000)
Timeline: 6 weeks
Guardian Oracle + Claim Verification Pipeline. When the owner's inactivity and grace period expires, the oracle notifies the lawyer (or beneficiaries directly if the lawyer does not act). The claim flow validates that the beneficiary matches the registered ZELF ID before enabling seed phrase reconstruction.
Architecture (6 weeks breakdown)
Tranche 3: Mainnet ($30,000)
Timeline: 6 weeks
In this phase, we will focus on developer SDK, wallet Integration, documentation & mainnet launch. Creation of developer tooling, wallet integration modules, and documentation. Includes demonstration application, mainnet deployment, and UX-ready onboarding flows.
Architecture (6 weeks breakdown)
Why Stellar?
We care about secure payments, rightful ownership, and transferring asset access rights to family when it matters most. So does Stellar.
- Low transaction costs: Heartbeat signals must be economically sustainable over years or decades.
- 5-second finality: Critical for time-sensitive claim processing.
- Soroban's Rust ecosystem: Direct code portability from our Solana Rust codebase.
- BLS12-381 support: Native support for the cryptographic curves our ZELF IDs require.
- Real-world financial infrastructure: Stellar's focus aligns with inheritance, a fundamentally real-world financial need.
Risk Mitigation
| Risk | Mitigation |
|---|---|
| Soroban contract security | Third-party audit by Ackee Blockchain or OtterSec before mainnet |
| ZK proof performance | Use native BLS12-381 support; fallback to off-chain verification with on-chain attestation |
| Oracle manipulation | Multi-signal attestation requirement; no single oracle can trigger inheritance |
| Regulatory uncertainty | Jurisdiction-aware policy framework; access-rights model avoids custody classification |
Open Source Commitment
We'll open-source everything Stellar-specific under MIT: contracts, heartbeat protocol, oracle interface, SDKs, demo app, docs.
ZELF ID architecture stays proprietary but ships as an SDK with a free tier for Stellar devs.
Disclaimer:
The terminology used across our site, documentation and videos is currently getting updated to:
- ZK Face Proof = HumanAuthn
- ZelfProof = ZELF ID
- ZK compression = QR Code
Dismiss any terminology that is not up to date.
$90k gets you: Soroban inheritance contracts, heartbeat protocol, oracle (we have a proof of concept), SDKs, demo app, and mainnet. We've got the biometrics; the rest gets built for Stellar.
Don't let your crypto die with you.