PR-TDR: Privacy-Preserving and Reliable Timed Data Release

Timed Data Release (TDR) is a practical security mechanism that safeguards data until a prescribed time has elapsed. However, existing TDR frameworks do not focus on reliability guarantees and lack formal security analysis. To this end, we propose PR-TDR, a novel framework that supports privacy-preserving and reliable timed data release while providing provable security properties. PR-TDR includes two novel contributions: a formal privacy-preserving design for TDR, named P-TDR and a reliable lifetime secret key management built on top of P-TDR that systematically empowers P-TDR with reliability. P-TDR prevents adversaries from accessing the data prior to the prescribed release time. At the core of the design of P-TDR, a group of decentralized peers, which operates under an honest-majority assumption, collaboratively takes charge of managing the lifetime secret key. Each peer stores a key share of the secret key. The proposed reliability layer that empowers P-TDR with reliability guarantees incorporates two carefully designed protocols that operate before the prescribed release time, namely the lifetime secret key auditing protocol and the lifetime secret key share recovery protocol. The auditing protocol enables a semi-honest auditor to confirm the availability of the lifetime secret key with the peers while not gaining any knowledge about the secret key itself. The recovery protocol allows peers that have lost their respective shares of the lifetime secret key to recover them with the help of other peers, ensuring that the lifetime secret key remains private. We provide formal security proof to demonstrate that PR-TDR satisfies the desired security properties. We implement our framework using Ethereum and our performance evaluations confirm that PR-TDR not only embodies the desired security properties but also operates efficiently.