Zelf Legacy: Biometric Inheritance Protocol for Stellar

Abstract

Zelf Legacy introduces a non-custodial inheritance infrastructure for digital assets built on Stellar and Soroban.

Users can maintain multiple self-custody wallets across trading, savings, and on-chain applications while ensuring that, in the event of post-mortem or prolonged inactivity, rightful beneficiaries can securely recover access rights without transferring assets into custody.

Instead of locking funds inside smart contracts, Zelf Legacy coordinates inheritance through programmable access-rights verification. Beneficiaries gain the ability to reconstruct wallet access only after predefined inheritance conditions are met, including inactivity verification, biometric authentication, and identity validation.

The system combines:

• Soroban smart contracts
• Heartbeat Protocol liveness verification
• Guardian Oracle coordination
• ZELF ID biometric identity infrastructure
• Shamir's Secret Sharing recovery architecture

No biometric templates are stored on centralized servers or databases. Assets remain in the original wallet throughout the inheritance lifecycle.

Zelf Legacy is powered by HumanAuthn, a biometric-rooted authentication and encryption primitive that regenerates ephemeral cryptographic keys from live facial verification. This architecture enables passwordless self-custody without exposing seed phrases or relying on custodial infrastructure.

The requested $40,000 grant will fund the development of:

• Soroban inheritance contracts
• Heartbeat Protocol infrastructure
• Guardian Oracle execution layer
• Stellar-native SDKs
• Developer tooling
• Testnet and mainnet deployment

All Stellar-specific infrastructure will be built natively for Soroban and open-sourced under MIT licensing.

Why This Matters for the Stellar Ecosystem

Stellar secures billions of dollars in self-custodied digital assets, yet the ecosystem lacks native inheritance infrastructure.

Without programmable inheritance mechanisms:

• assets can become permanently inaccessible
• families may lose access to funds
• long-term self-custody adoption becomes harder for mainstream users

Zelf Legacy introduces a non-custodial inheritance coordination layer designed specifically for the Stellar ecosystem.

The protocol expands Stellar's capabilities beyond payments into long-term digital asset continuity, rightful ownership transfer, and programmable beneficiary coordination.

This positions Stellar as infrastructure not only for payments, but also for generational digital asset ownership.

What Is Zelf?

Zelf is a cybersecurity and self-custody infrastructure platform powered by HumanAuthn, a biometric-rooted authentication and encryption primitive.

Unlike traditional authentication systems that anchor trust in hardware devices or custodial databases, HumanAuthn replaces device-rooted authentication with biometric-rooted cryptographic ephemeral key regeneration.

A live biometric scan regenerates a temporary encryption key used to decrypt wallet credentials, eliminating the need for:

• seed phrases
• password storage
• custodial recovery systems
• persistent biometric templates

This creates a device-agnostic identity layer designed for self-custody, authentication, and secure digital inheritance.

Zelf is available on: Web Extension, iOS, and Android.

What Is Zelf Legacy?

Zelf Legacy addresses one of the largest unresolved problems in self-custody:

What happens to digital assets when their owner dies or becomes permanently inactive?

Most crypto inheritance systems rely on:

• custodial escrow
• multisig dependency
• smart-contract fund locking, or
• manual legal coordination

Zelf Legacy introduces a different model. Instead of transferring assets into custody, the protocol coordinates inheritance through programmable access-rights activation.

Inheritance execution only begins after:

• inactivity verification
• grace-period expiration
• beneficiary biometric verification
• government-issued identity validation

Assets remain in the original wallet throughout the entire process.

Protocol Flow Diagram

Step 1: Create an Inheritance Policy

Users activate Legacy Mode inside the Zelf app and designate beneficiaries through ZELF ID biometric identity binding.

Each beneficiary is linked to an encrypted inheritance policy that defines:

• inheritance thresholds
• beneficiary consensus rules
• legal coordination preferences
• recovery conditions

The inheritance architecture combines:

• Soroban smart contracts
• ZELF ID biometric verification
• IPFS and Arweave decentralized storage
• Shamir's Secret Sharing recovery logic

Policy metadata is encrypted and stored off-chain while Soroban records only verification state and execution logic.

Users can configure:

• 2-of-3 or 3-of-5 recovery thresholds
• lawyer participation
• direct beneficiary execution
• multi-beneficiary inheritance structures

Step 2: Heartbeat Protocol

Zelf Legacy introduces a Heartbeat Protocol: a cryptographic liveness verification system anchored to Soroban smart contracts.

Instead of continuously tracking users or relying on custodial inactivity monitoring, the protocol enables periodic proof-of-life verification directly from the Zelf app.

Each heartbeat:

• verifies live user presence
• resets the inheritance inactivity timer
• emits a signed Soroban event
• updates the inheritance execution state

The protocol is privacy-preserving by design:

• heartbeat credentials remain private
• no public inheritance registry exists
• no behavioral tracking is required
• liveness detection prevents spoofing attacks

Users define:

• inactivity windows (30 days to 24 months)
• grace periods
• inheritance activation conditions

Heartbeat history is compressed through verifiable credential architecture and Merkle-proof validation, reducing on-chain storage requirements by 100–1000x compared to traditional state storage models.

If heartbeat expiration and grace-period thresholds are reached, the inheritance execution pipeline begins.

This transforms inheritance from a manual legal process into programmable self-custody infrastructure.

Step 3: Access Rights Recovery

Once inactivity and grace-period conditions are satisfied, beneficiaries can initiate the inheritance claim process.

Claim execution requires three verification layers:

Design Principles

Zelf Legacy is designed around the following principles:

• Non-custodial by default
• Assets remain in the original wallet
• No biometric templates stored
• Privacy-preserving liveness verification
• Human-rooted authentication
• Programmable inheritance execution
• Off-chain encrypted metadata
• Soroban-native coordination
• Long-term cost sustainability

Technical Architecture

Five coordinated layers power inheritance execution without moving assets into custody.

The HumanAuthn engine and ZELF ID infrastructure are already operational.

The Stellar grant focuses on building the inheritance coordination layer natively on Soroban, including:

• inheritance registry contracts
• Heartbeat Protocol infrastructure
• Guardian Oracle coordination
• claim verification pipeline
• Stellar SDK integration
• developer tooling

The architecture is divided into four layers:

Security & Privacy

Zelf Legacy is designed to minimize custodial risk and centralized attack surfaces.

Key security properties include:

• no biometric templates stored
• private keys remain off-chain
• encrypted off-chain metadata
• liveness verification with spoof resistance
• programmable inactivity thresholds
• decentralized storage through IPFS and Arweave
• cryptographic claim verification through Soroban

The protocol coordinates access-right recovery without taking custody of user assets.

Why Stellar?

Zelf Legacy aligns directly with Stellar's strengths in payments, identity, ownership verification, and real-world financial coordination.

Inheritance is fundamentally a real-world financial infrastructure problem. Stellar provides the technical foundations required to make programmable inheritance economically sustainable and globally accessible.

Key reasons for choosing Stellar include:

• Low transaction costs: Heartbeat verification must remain economically sustainable over years or decades.
• Fast finality: Time-sensitive inheritance execution requires reliable settlement guarantees.
• Soroban's Rust ecosystem: Enables direct portability from existing Rust-based infrastructure.
• Native BLS12-381 support: Critical for on-chain verification of ZELF ID cryptographic primitives.
• Real-world financial focus: Stellar's ecosystem aligns closely with long-term inheritance infrastructure and rightful ownership systems.

Stellar Integration Plan

Zelf Legacy is being built specifically around Soroban's authorization, storage, and cryptographic architecture.

Rather than porting an existing EVM inheritance system, the protocol leverages Stellar-specific components to optimize long-term storage efficiency, low-cost liveness verification, programmable inheritance execution, biometric entitlement verification, and real-world financial coordination.

Stellar-Specific Building Blocks

Stellar Integration Flow

Data flow showing exactly how Stellar components participate in the inheritance lifecycle:

Open Source Commitment

All Stellar-specific infrastructure developed through this grant will be released under MIT licensing, including:

• Soroban smart contracts
• Heartbeat Protocol infrastructure
• Guardian Oracle interfaces
• SDKs
• demo applications
• developer documentation

The HumanAuthn and ZELF ID core architecture will remain proprietary while being exposed through developer SDKs with free-tier access for Stellar ecosystem developers.