Equitable key escrow with limited time span (Or, how to enforce time expiration cryptographically)

Abstract

With equitable key escrow the control of society over the individual and the control of the individual over society are shared fairly. In particular, the control is limited to speci ed time periods. We consider two applications: time controlled key escrow and time controlled auctions with closed bids. In the rst the individual cannot be targeted outside the period authorized by the court. In the second the individual cannot withhold his closed bid beyond the bidding period. We propose two protocols, one for each application. We do not require the use of tamper-proof devices.