4 ms·
Show HN: Shardium – open-source "Dead Man's Switch" for crypto inheritance
Hi HN, I'm Max.
I built this because I was terrified that if I die tomorrow, my family gets nothing. The existing solutions were either trusting a centralized custodian or complex hardware setups.
Shardium is a client-side tool that splits your seed phrase into 3 shards using Shamir's Secret Sharing.
Shard A: You keep.
Shard B: You give to a beneficiary (PDF).
Shard C: We hold (or you self-host).
It works as a dead man's switch: If you are inactive for 90 days (email ping), Shard C is released to your beneficiary. They combine B + C to recover the funds.
The Stack:
secrets.js-grempe for the math.
FastAPI + PostgreSQL backend.
Client-side encryption (seed never hits the network).
It is 100% Open Source and MIT Licensed. You can self-host it for free ($0), or use the managed version.
I'd love your feedback on the security model. Roast my code here: https://github.com/pyoneerC/shardium https://github.com/pyoneerC/shardium
- ycombinatrix 9mo agoI prefer to do a 4 shares / 2 needed for recovery. I keep 2 on different storage media, 1 with a trusted beneficiary, 1 with a different trusted beneficiary. This does mean that the beneficiaries can collude to rob me tho. But it is simpler than running & trusting some kind of live service imo.
- cylinderthought 9mo agorunning 4-of-2 definitely removes the service dependency. you highlighted exactly the "bug" i wanted to patch though: the collusion risk. if beneficiary A and B have a beer together, you get rugged. the "live service" here acts purely as a time-lock. beneficiaries can't collude to rob you today because the 3rd shard isn't released until the dead man's switch actually triggers. it protects you from your own friends.
- ycombinatrix 9mo agoYou should consider highlighting that this can be used for way more than crypto wallets. The seed phrase can be used to restore a GPG key, a FIDO2 authenticator including SSH/WebAuthn, etc.
- cylinderthought 9mo ago100%. i actually use it for my gpg keys too. i need to make that clearer on the landing page so it doesn't look like a "crypto-only" tool. recovering ssh/fido2 backups is a huge use case. thanks for the feedback
- reachableceo 9mo agoWhy not use Vaultwatden for this ? It has a built in dead man switch recovery system.
- cylinderthought 9mo agobig fan of vaultwarden (i self-host it). the main difference is architecture: shardium splits the secret (shamir) so the server never holds the full data, whereas vaultwarden holds the full encrypted vault. also the "grandma factor": getting non-tech family to setup a vaultwarden account was friction. this is just "find paper in drawer, scan qr".