Last Safe

The last safe you'll ever need. Shared only with the ones who need it. Secure, decentralized, peer to peer digital inheritance. You own your data. No servers. No middlemen.

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Last Safe

The last safe you'll ever need. Shared only with the ones who need it. Secure, fully decentralized digital inheritance — no servers, no middlemen, no single point of failure.

Inspiration

Death is the oldest unsolved software problem. Every year, families are locked out of crypto wallets, email accounts, and financial systems simply because the person who knew the passwords is gone. Today's solutions are broken in opposite directions: cloud vaults depend on companies outlived by their users, and lawyers charge thousands for trivial paperwork.

We kept asking one question: how do you hand off secrets automatically, only when you're truly gone — without trusting any third-party? Nobody had a clean answer. So we built one.

"When you're gone, so is everything you knew."

What it does

Last Safe is a peer-to-peer application where your trusted contacts collectively hold a cryptographic key to your estate. No single guardian can access your secrets alone — and nothing opens until you've been silent long enough.

  1. You encrypt your estate — passwords, wallet seed phrases, legal documents, photographs, personal letters — anything that only you hold today.
  2. Key split across N guardians — Shamir's Secret Sharing divides the decryption key into shares distributed to your chosen people.
  3. You send a heartbeat while alive — a periodic proof-of-liveness that keeps the vault sealed.
  4. Dead man's switch — utilizing Solana and Lit Protocol, decryption is possible only after the predetermined time-lock.
  5. Estate revealed to guardians — once the threshold of shares is assembled and time-lock has elapsed, each guardian decrypts locally. No server is ever involved.

How we built it

The entire system is built on three interlocking primitives: threshold secret sharing (Shamir's Secret Sharing splits the decryption key into N shares, requiring M to reconstruct), end-to-end encryption (AES-256 encrypts the estate stored on the devices), and a dead man's switch (a decentralized protocol based on Solana and Lit Protocol which prevents malicious heirs from accessing the estate prematurely).

The app is fully peer-to-peer — guardians communicate directly without routing data through any servers while the time-lock lives on P2P protocols. We use a DHT-based overlay network for peer discovery and relay, with encrypted channels for all share distribution. The heartbeat mechanism relies on Lit Protocol's secret sharing conditioned on a Solana smart contract.

Stack: Pear API· React Native · Node.js · Rust · Solana (smart contracts) · Python

Challenges we ran into

Defining "gone" — Proving liveness is easy. Proving death without a trusted oracle is hard. We had to design a heartbeat protocol that is actually decentralized -- made possible by combining two decentralized protocols.

Guardian coordination — Requiring M-of-N guardians to come online simultaneously is a UX nightmare. We built an asynchronous unlock flow where shares accumulate over time rather than requiring a live session.

Key recovery without a server — If a guardian loses their device, their share is gone. We designed a social recovery mechanism — guardians can re-shard among themselves using the existing quorum, without ever reconstructing the master secret.

Accomplishments that we're proud of

We built a working end-to-end prototype in under 48 hours — an encrypted vault, a functioning key-split across simulated guardians, a heartbeat monitor, and an unlock flow that requires no server involvement at any step. Zero plaintext ever leaves the owner's device.

We're especially proud of the asynchronous unlock protocol: guardians don't have to coordinate in real time. Shares accumulate on the peer network until the threshold is met, then decryption happens locally on each guardian's device independently.

We realized that building a decentralized time-lock is paradoxical: storing keys on-chain guarantees instant theft, while using off-chain servers creates a centralized point of failure. Our breakthrough was decoupling the clock from the execution by using a Solana smart contract purely as a tamper-proof heartbeat monitor, forcing Lit Protocol's MPC network to independently verify the "dead" state before reconstructing the encrypted keys.

The UX for something this cryptographically complex is genuinely simple — if you can name three people you trust, you can set up your Last Safe in under five minutes.

What we learned

We had not coded a smart contract before. It was a learning experience to request SOL airdrops and deploy our contract on the actual blockchain.

What's next for Last Safe

The prototype proves the model works. Now we want to harden it into something people can rely on for the rest of their lives.

Biometric heartbeat — passive liveness via device usage signals, removing the need for manual check-ins.

Legal integration — optional notarization layer that wraps estate documents in a legally recognized format before encryption.

Open protocol — publish the heartbeat and key-distribution spec openly so others can build compatible vaults. The smart contract should be audited.

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