SeCritMass: Threshold Secret Petitions

We introduce the notion of an $n$-threshold secret petition, in which users add encrypted signatures to a petition, and the signatures are decrypted if and only if at least $n$ signatures have been gathered. This solves the coordination problem in which users wish to sign a petition or commit to a cause, but do not want to be identified as having signed it before enough others have signed it too. We present an implementation of such a petition based on the ElGamal cryptosystem. Applications include reporting misconduct in situations were complainants hesitate to come forward alone, such as in allegations of sexual harassment or police brutality.