Committed entry lists
Change the list? The draw stops.
Before a Beaver draw selects anybody, the final entry list is frozen and its fingerprint is published. After that, the list cannot be quietly changed. If it is changed, the draw refuses to run.
What is a commitment?
A commitment is a short value derived from something larger, published now, that binds you to that larger thing later.
For a draw, the larger thing is the full eligible entry list. Beaver computes a cryptographic fingerprint of it, a hash, and publishes that fingerprint before selection. The list itself can be checked against the fingerprint at any time afterwards.
ENTRY LIST (1,000 entries)
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HASH FUNCTION
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FINGERPRINT 9f1c...a7e2 <- published before the draw
The fingerprint above is an example value, not a real Beaver draw.
Why before selection?
Timing is the whole point. A fingerprint published after the winner is known proves nothing: the list could have been adjusted to suit the result and then fingerprinted.
Published before selection, the fingerprint pins the list down while nobody, including the operator, knows who will win.
Published before. Verifiable after.
What the commitment covers
The final eligible population the winner is drawn from. That includes accepted free entries, from the online or postal route, because they sit in the same pool as paid entries.
Reserved tickets that were never paid for are released before the list closes, so they are not in it.
Tamper refusal
Before selection, Beaver checks the entry list against its published commitment. If a single entry has been added, removed or altered, the fingerprints do not match and the draw does not run.
That is the product behaviour. Not a warning. Not a line in a report. The draw stops.
Live Tamper refusal is part of the live draw engine.
What a commitment does not prove
It proves the list did not change. It does not prove that every entry on it was eligible under the promotion's terms, that the free route was adequately promoted or that the promotion is lawfully structured.
Those questions belong to the operator's wider compliance, covered in UK prize draw compliance.
Try it
Commit a list. Then change one entry.
Run the draw, then press "Change one entry after the commit" and check it. The fingerprint no longer matches, and the result is refused.
- 1Commit the entries
- 2Reveal the randomness
- 3Select the winner
- 4Check it yourself
Entry list 1,000 entries
Commitment (SHA-256 of the list)
Not committed yet
Randomness
Named before the draw, published after. Nobody knows it yet.
Winning ticket
Pending
Verification
- Entry list matches its commitment
- Randomness was named before it existed
- Winner recomputes from the published values
Press Run the draw to start.
A demonstration of the method, running in your browser. It is not a live Beaver draw, and it does not use Beaver's exact algorithm or randomness source. The "randomness" here is a stand-in for a public value published after the entries are committed.