Puzzle Proof Generator

Use this tool to show that you knew a puzzle answer at the time you posted your proof, without posting the answer itself. The calculation takes place entirely in your browser; the answer is not sent to the National Cipher Challenge website by this tool.

Keep the puzzle identifier and forum username exactly the same when checking a proof later. Answers are compared without regard to upper/lower case and with spaces removed only from the beginning and end.

Information to prove or check Puzzle or challenge identifier

For example: Challenge 4B or Puzzle 17.

Forum username

This tool creates a unique proof for each forum username. To prove your own solve, use your username exactly as it appears on the forum. To check a proof, use the username of the person who posted it.

Puzzle answer

The answer stays in this browser. All whitespace is removed, then it is Unicode-normalised (NFC) and converted to uppercase before hashing.

Show answer while typing

Your proof Proof to publish in the forum

The proof contains a version label and a SHA-256 digest, but not the answer itself. If the set of possible answers is small, someone may still recover the answer by trying possibilities, so use a full plaintext answer rather than a short key where possible.

Check a published proof Published proof

How the proof is calculated

The tool forms a JSON array containing the fixed scheme name PROOFv1, the puzzle identifier, forum username and normalised answer, encodes it as UTF-8, and calculates its SHA-256 digest using the browser's built-in Web Crypto API.