Score freezing
Also known as: Score sealing · SHA-256 hash · Cryptographic seal
Sealing the delivered scores with a cryptographic hash before seeing the results, so no score can be altered once the events are known.
At Zarv
SHA-256 hash of the score file, handed over before the outcome labels.
In a blind test the scores go out before the answer key — but how do you prove, afterward, that the score file was not touched between one send and the next? Score freezing settles it with cryptography: when it delivers the scores, Zarv also delivers the SHA-256 hash of the file, a fixed-length fingerprint that changes completely if a single value is altered.
With the hash in hand, you can later receive the outcome labels and run the match with confidence: any edit to the score file would produce a different hash, and the difference would be obvious. That is what lets you state, verifiably, that no score changed after the events became known.
Frequently asked questions
How do you guarantee the scores were not altered afterward?
By delivering, alongside the score file, its SHA-256 hash — a cryptographic fingerprint. Since any change to the file changes the hash completely, you can verify the scores are exactly the ones delivered before the results.