Provably Fair

What is drand? drand (pronounced “dee-rand”) is a decentralized, verifiable, and unpredictable randomness generator. Its random numbers are not generated by any single entity, but are collectively computed in real time by the “League of Entropy“—a global consortium of leading tech organizations and academic institutions, including Cloudflare (the global network security giant), Ethereum Foundation, Protocol Labs, and EPFL (Swiss Federal Institute of Technology Lausanne). Consequently, it mathematically guarantees unpredictability, immutability, and publicly verifiable fairness and transparency.

🌟 Overview

cloudflare-drand-verifier is a serverless, single-page random number generation system. Every calculation is performed directly within each user’s browser, ensuring that the generated results cannot be manipulated by anyone. It serves as a decentralized and provably fair randomness verification tool.

The system combines the Cloudflare Distributed Randomness Beacon with the drand network. By locking in a future timestamp before the draw takes place, it ensures that no one can predict or manipulate the outcome before the randomness is generated.

Once the draw concludes, a unique permalink is generated for that specific draw page. Anyone can recalculate and verify the results at any time using the computation report provided on the permalink page along with public drand data—ensuring complete transparency and immutability.

💡 Quick Tip: The simplest way to verify is to copy the entire computation report from the page and paste it into any AI tool (such as ChatGPT, Gemini, Grok, or DeepSeek) and ask it to recalculate and check the steps for you!

The verifier codebase has been open-sourced on GitHub, allowing anyone to review it.

Learn more:

🛠️ How It Works

1.Draw Data Locking (Pre-commitment)

Before the draw begins, parameters such as the Draw ID, draw time, and total number of tickets are locked. Once set, these parameters cannot be altered in any way.

2.Future Round Locking

The system automatically calculates the drand round corresponding to the chosen draw time and enforces selecting the next consecutive round. Because this round has not yet been generated at the time of commitment, it is mathematically impossible for anyone to foresee the outcome.

3.Unbiased Rejection Sampling

After retrieving the SHA-256 hash of the drand round signature, the system uses an Unbiased Rejection Sampling algorithm to derive the winning numbers. This completely eliminates modulo bias inherent in traditional arithmetic, ensuring every single number has an identical probability of being selected.

4.Provable Fairness & Easy Verification

Once the draw concludes, a unique permalink is generated for that specific draw page. Anyone can recalculate and verify the results using the computation report on the permalink page alongside public drand data.