Show HN: Double blind entropy using Drand for verifiably fair randomness

Source: Hacker News

Overview

The only way to obtain a trust‑less random value is to have it distributed and time‑locked across three parties: the player, the server, and a future entropy source.

How It Works

1. Commit Phase

   • The player commits to a secret by sending the hash of that secret (the player‑hash) to the server.
   • The server responds with the hash of its own secret (the server‑hash) and the round number of a future drand randomness beacon that will be used. In the demo, the future round occurs 10 seconds later.

2. Reveal Phase (after the specified drand round)

   • Both the player and the server reveal their original secrets.
   • The final random number is generated from the concatenation:

   player‑seed : server‑seed : drand‑signature

   where the drand‑signature is the beacon output for the chosen round.

Verification

All verification is purely mathematical, making the process truly trust‑less:

1. The player‑seed must match the previously committed player‑hash.
2. The server‑seed must match the previously committed server‑hash.
3. The drand‑signature is not available at commit time (time‑locked) and becomes publicly accessible only at reveal time.
4. The generated random number is deterministic after the reveal but remains unknown and unpredictable beforehand.
5. No party can influence the final outcome, eliminating any “last‑look” advantage.

Potential Applications

This scheme can be applied to any system that requires provably fair randomness, such as:

• Online games
• Lottery and gambling platforms
• Any other service that wants fairness by design rather than by trust

References

• Discussion on Hacker News: (6 points, 6 comments)