SilentDelivery: Practical Timed-Delivery of Private Information Using Smart Contracts

This article proposes
SilentDelivery
, a secure, scalable, and cost-efficient protocol for implementing timed information delivery service in a decentralized blockchain network.
SilentDelivery
employs a novel combination of threshold secret sharing and decentralized smart contracts. The protocol maintains shares of the decryption key of the private information of an information sender using a group of mailman recruited in a blockchain network before the specified future time-frame and restores the information to the information recipient at the required time-frame. To tackle the key challenges that limit the security and scalability of the protocol,
SilentDelivery
incorporates two novel countermeasure strategies. The first strategy, namely
silent recruitment
, enables a mailman to get recruited by a sender
silently
without the knowledge of any third party. The second strategy, namely
dual-mode execution
, makes the protocol run in a lightweight mode by default, where the cost of running smart contracts is significantly reduced. We rigorously analyze the security of
SilentDelivery
and implement the protocol over the Ethereum official test network. The results demonstrate that
SilentDelivery
is more secure and scalable compared to the state of the art and reduces the cost of running smart contracts by 85 percent.