  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.
