Threshold cryptography is the art of chopping a secret into little bits, so that the secret can only be learned by possessing more than a threshold number of those bits.

This is useful, for example, if you want to share a secret with a group of people (who each will receive/carry a part of the secret) and you want to make sure that no single individual can learn the secret unless two or more people combine their secret parts (depending on how many the threshold defines) to learn the secret. Practically, this can be found in military (and other) realms, where launch codes tend to be protected by threshold cryptography – so that no individual can initiate a launch, but when a launch-controller and his superior both enter their secret keys, that creates a combined and valid authorization code.

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