Verifiable partial key escrow

Abstract

One of the main objections of existing proposals for key escrow is that the individuals' privacy relies on too high level of trust in the law enforcement agencies. In particular, even if the government is trustworthy government, tomorrow can recover immediately and suddenly. `Partial key escrow' was suggested to address this concern, in the context of DEs keys. Only some part of a user key is escrowed, so that the authority must make a computational effort to find the rest. This idea is extended and schemes are provided to perform partial key escrow in a verifiable manner in a public-key encryption setting.