DBL－可否認的區塊鏈帳本

DBL: Deniable Blockchain Ledger

陳炫豪(Hsuan-Hao Chen) ； 紀博文(Po-Wen Chi)

《資訊安全通訊》 25卷4期 (2019/11) Pp. 1-16

摘要

本文建構了一個可否認的區塊鏈帳本，賦予原本具有不可修改性的區塊鏈可否認的性質，讓此區塊鏈帳本的擁有者能夠藉由產生合法且無法被識破的假交易區塊複本來否認原始的區塊鏈帳本，以防惡意的使用者對帳本的擁有者進行暴力脅迫，也讓區塊鏈上的內容能夠被修改及遺忘。可否認的區塊鏈帳本架構利用了區塊鏈的型式以及Chameleon Hash的雜湊碰撞來建構成一個可以修改交易紀錄但仍舊保有相同的雜湊函數值的區塊鏈，透過重複使用雜湊碰撞並產生新區塊的演算法來提供其他使用者假的交易紀錄複本，雖然其他使用者可以發現每份複本皆不相同，但由於不同的區塊前後的雜湊函數值皆合法，所以他們無法證明哪一份複本為真、哪一份複本為假。我們也介紹了兩種使用可否認的區塊鏈帳本的情況，分別是交易紀錄相關的使用者皆為一般使用者的情況以及交易紀錄相關的使用者為惡意使用者之同夥的情況，並提供兩種演算法來應用相對應的狀況。最後我們目前也在進行此架構的實作及測試，期望未來這個可否認的區塊鏈帳本能夠應用到現實社會。

關鍵字

區塊鏈 ； 可否認性 ； Chameleon Hash

並列摘要

In this paper, we construct a deniable blockchain ledger (DBL), which enhances blockchain with a new feature, deniability. The owner of the deniable blockchain ledger can produce a new blockchain copied from the original blockchain and replace some blocks with fake blocks. So, the original transaction data are hidden and our scheme can keep transaction privacy from outside coercion. The transaction data on DBL can also be redacted or be forgotten. Our DBL construction uses the Chameleon Hash as the hash function to make a block be redactable since it is easy to find a collision with the trapdoor. So, the hash value of the redacted block is still the same to the original block and the original following block can still associated to the generated fake block. Even an attacker can collect multiple blockchains, it is impossible for the attacker to determine which blockchain is the original one. We also provide two scenarios and the corresponding algorithms of generating fake blocks. One is that every user is normal user and the other is that some users are compromised. We are currently implementing the DBL and hope that our construction can protect data privacy in the blockchain.

並列關鍵字

Blockchain ； Deniability ； Chameleon Hash

參考文獻

Pilkington, Marc. "11 Blockchain technology: principles and applications." Research handbook on digital transformations 225 (2016).

Haber, Stuart, and W. Scott Stornetta. "How to time-stamp a digital document." Conference on the Theory and Application of Cryptography. Springer, Berlin, Heidelberg, 1990.

Nakamoto, Satoshi. "Bitcoin: A peer-to-peer electronic cash system." (2008).

Ateniese, Giuseppe, et al. "Redactable blockchain–or–rewriting history in bitcoin and friends." 2017 IEEE European Symposium on Security and Privacy (EuroS&P). IEEE, 2017.

Krawczyk, Hugo Mario, and Tal D. Rabin. "Chameleon hashing and signatures." U.S. Patent No. 6,108,783. 22 Aug. 2000.