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Send Message to the Future? Blockchain-based Time Machines for Decentralized Reveal of Locked Information

Zhuolun Li, Srijoni Majumdar, Evangelos Pournaras

TL;DR

A new practical timed-release cryptography system that “sends messages in the future” with highly accurate decryption times is presented, and a novel secret sharing scheme with verifiable information reveal is devised on smart contracts.

Abstract

Conditional information reveal systems automate the release of information upon meeting specific predefined conditions, such as time or location. This paper introduces a breakthrough in the understanding, design, and application of conditional information reveal systems that are highly secure and decentralized. By designing a new practical timed-release cryptography system and a secret sharing scheme with reveal-verifiability, a novel data sharing system is devised on the blockchain that "sends messages in the future" with highly accurate decryption times. Notably, the proposed secret sharing scheme applies to other applications requiring verifiability of revealed secret shares. This paper provides a complete evaluation portfolio of this pioneering paradigm, including analytical results, a validation of its robustness in the Tamarin Prover and a performance evaluation of a real-world, open-source system prototype deployed across the globe. Using real-world election data, we also demonstrate the applicability of this innovative system in e-voting, illustrating its capacity to secure and ensure fair electronic voting processes.

Send Message to the Future? Blockchain-based Time Machines for Decentralized Reveal of Locked Information

TL;DR

A new practical timed-release cryptography system that “sends messages in the future” with highly accurate decryption times is presented, and a novel secret sharing scheme with verifiable information reveal is devised on smart contracts.

Abstract

Conditional information reveal systems automate the release of information upon meeting specific predefined conditions, such as time or location. This paper introduces a breakthrough in the understanding, design, and application of conditional information reveal systems that are highly secure and decentralized. By designing a new practical timed-release cryptography system and a secret sharing scheme with reveal-verifiability, a novel data sharing system is devised on the blockchain that "sends messages in the future" with highly accurate decryption times. Notably, the proposed secret sharing scheme applies to other applications requiring verifiability of revealed secret shares. This paper provides a complete evaluation portfolio of this pioneering paradigm, including analytical results, a validation of its robustness in the Tamarin Prover and a performance evaluation of a real-world, open-source system prototype deployed across the globe. Using real-world election data, we also demonstrate the applicability of this innovative system in e-voting, illustrating its capacity to secure and ensure fair electronic voting processes.
Paper Structure (39 sections, 4 theorems, 5 equations, 9 figures, 2 tables)

This paper contains 39 sections, 4 theorems, 5 equations, 9 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Related Work
  3. Timed-Release Cryptography Systems
  4. The Time Lock Puzzles Approach
  5. The Secret Holders Approach
  6. The reveal-verifiability problem
  7. Comparison of Existing Secret Holder Approaches
  8. Secret Sharing Schemes for Secret Holders Approach
  9. Required Background
  10. Diffie-Hellman Key Exchange
  11. Bilinear Pairings
  12. Secret Sharing with Reveal-Verifiability on Public Communication Channel
  13. Problem Modeling and Assumptions
  14. Design
  15. Applying to Timed Release Cryptography
  16. ...and 24 more sections

Key Result

Lemma 1

When $n=3, t=2$, For any PPT external adversaries$\mathcal{A}$ that have access to the public knowledge $(g_1, g_2, pk_1, pk_2, pk_3, g_1^r, g_2^r, \alpha_{3})$ and at most one secret share $(s_i, i\in\{1,2,3\})$, the probability of knowing $k$ is negligible.

Figures (9)

  • Figure 1: Bitcoin block time distribution from July 2022 to July 2023
  • Figure 2: An example of the proposed secret sharing method with four secret holders
  • Figure 3: The high-level process of sending a timed-release message
  • Figure 4: Example workflow in the view of on-chain activities
  • Figure 5: Modules in the decentralized architecture for conditional information reveal systems using smart contract and secret sharing
  • ...and 4 more figures

Theorems & Definitions (10)

  • Definition 1
  • Definition 2
  • Lemma 1
  • proof
  • Lemma 2
  • proof
  • Lemma 3
  • proof
  • Lemma 4
  • proof