I Told You Tomorrow: Practical Time-Locked Secrets using Smart Contracts

Abstract

A Time-Lock enables the release of a secret at a future point in time. Many approaches implement Time-Locks as cryptographic puzzles, binding the recovery of the secret to the solution of the puzzle. Since the time required to find the puzzle's solution may vary due to a multitude of factors, including the computational effort spent, these solutions may not suit all scenarios.To overcome this limitation, we propose I Told You Tomorrow (ITYT), a novel way of implementing time-locked secrets based on smart contracts. ITYT relies on the blockchain to measure the elapse of time, and it combines threshold cryptography with economic incentives and penalties to replace cryptographic puzzles.We implement a prototype of ITYT on top of the Ethereum blockchain. The prototype leverages secure Multi-Party Computation to avoid any single point of trust. We also analyze resiliency to attacks with the help of economic game theory, in the context of rational adversaries. The experiments demonstrate the low cost and limited resource consumption associated with our approach. CCS CONCEPTS• Security and privacy → Security services.

Securing blockchain-based timed data release against adversarial attacks1

“…Second, adjusted by ξ , for P j , Rep(P j ) is gradually built up when P j honestly contributes in the protocol and it is rapidly reduced when P j dishonestly deviates the protocol. Third, to make the initial measure of each peer as the value of 1 2 , in the denominator, we assign two constants +1 and −1. An Example: For instance, if P j has engaged in 12 timed-release services, wherein he/she honestly followed the protocol 8 times and dishonestly deviated the protocol 4 times, the reputation is measured by Rep(P j ) = (8+1) (8+1)+1+3 * 4 = 0.41, which indicates that for the incoming service engagement, P j holds 0.41 likelihood to follow the service.…”

“…An Example: For instance, if P j has engaged in 12 timed-release services, wherein he/she honestly followed the protocol 8 times and dishonestly deviated the protocol 4 times, the reputation is measured by Rep(P j ) = (8+1) (8+1)+1+3 * 4 = 0.41, which indicates that for the incoming service engagement, P j holds 0.41 likelihood to follow the service. In particular, for a peer who does not hold any past observations, the reputation score is initialized with 1 2 . With our proposed reputation measure (Equation ( 8)) in hand, we next uncover our basic reputationaware timed data release design.…”

Delegated Proof of Accessibility (DPoAC): A Novel Consensus Protocol for Blockchain Systems

“…Threshold cryptography [5,6] allows a secret-owner to share a secret with a set of users. A (k, n)-threshold approach creates and distributes n shares of the secret among the The security evaluation of any consensus protocol is often assessed with this characteristicbased approach, which involves the demonstration of the process to satisfy certain criteria that include agreement, validity, and termination.…”

“…Threshold cryptography [5,6] allows a secret-owner to share a secret with a set of users. A (k, n)-threshold approach creates and distributes n shares of the secret among the parties [7].…”

“…A certain amount of shares is required to uncover the secret through SSS. This is referred to as the threshold, and it denotes the minimum necessary of shares required to reveal the secret [5]. To better understand the SSS scheme, the secret is some data S that are decomposed into n distinct parts, S 1 , S 2 , .…”