  A powerful feature in mechanism design is the ability to irrevocably commit
to the rules of a mechanism. Commitment is achieved by public declaration,
which enables players to verify incentive properties in advance and the outcome
in retrospect. However, public declaration can reveal superfluous information
that the mechanism designer might prefer not to disclose, such as her target
function or private costs. Avoiding this may be possible via a trusted
mediator; however, the availability of a trusted mediator, especially if
mechanism secrecy must be maintained for years, might be unrealistic. We
propose a new approach to commitment, and show how to commit to, and run, any
given mechanism without disclosing it, while enabling the verification of
incentive properties and the outcome -- all without the need for any mediators.
Our framework is based on zero-knowledge proofs -- a cornerstone of modern
cryptographic theory. Applications include non-mediated bargaining with hidden
yet binding offers.
