All implementations of verifiable mix-nets provide computational privacy only, because the audit information published is encrypted using some public key algorithm. Consequently, at some time in the future, when the underlying cryptographic assumption is broken, privacy is violated, and each output message can be traced back to its input. We address this problem by presenting a mix-net that uses a homomorphic, unconditionally hiding commitment scheme to encrypt the audit information, implying unconditional or everlasting privacy towards the public. The correctness of our mix-net is guaranteed with overwhelming probability even if all authorities conspire, under the assumption that the commitment scheme is computationally binding until the mixing process has ended. An implication of our result is that many current applications that use mix-nets can be upgraded to unconditional privacy.
展开▼
