NIZKs with an Untrusted CRS: Security in the Face of Parameter Subversion
Résumé
Motivated by the subversion of ``trusted'' public parameters in mass-surveillance activities, this paper studies the security of NIZKs in the presence of a maliciously chosen common reference string. We provide definitions for subversion soundness, subversion witness indistinguishability and subversion zero knowledge. We then provide both negative and positive results, showing that certain combinations of goals are unachievable but giving protocols to achieve other combinations.