Academic journal article Harvard Journal of Law & Technology

Application of Zero-Knowledge Proof in Resolving Disputes of Privileged Documents in E-Discovery

Academic journal article Harvard Journal of Law & Technology

Application of Zero-Knowledge Proof in Resolving Disputes of Privileged Documents in E-Discovery

Article excerpt

TABLE OF CONTENTS    I. INTRODUCTION                                                    633  II. DISPUTES SURROUNDING PRIVILEGED DOCUMENTS PRESENT A CUMBERSOME  636      TRUST PROBLEM FOR ALL PARTIES INVOLVED III. ZERO-KNOWLEDGE PROOF ENABLES VALIDATION OF A STATEMENT WITHOUT  639      REVEALING ANY OTHER INFORMATION  IV. SOLVING THE TRUST PROBLEM IN PRIVILEGE LOG DISPUTES WITH        643      ZERO-KNOWLEDGE PROOF      A. The Millionaire Model                                        643        1. A Review of Machine Learning in Technology-Assisted        644           Review in e-Discovery        2. Case-Specific Machine Learning Algorithms                  649        3. Generic Machine Learning Algorithms                        651      B. The Sudoku Model                                             653   V. CONCLUSION                                                      655 


In recent years, as e-discovery of electronically stored information ("ESI") has become widely adopted, the number of disputes over privileged documents have also exploded. Resolving these disputes in large civil cases often involves lengthy court adjudications, in camera reviews, and sometimes even special masters appointments to oversee the process. (1) As one judge put it, "such a situation is detrimental to the litigants, the courts, and our system of justice." (2) In addition to the sheer amount of work involved, judges are also tasked with striking the delicate balance between imposing high financial costs on the privilege-claiming party by demanding detailed descriptions of the claimed documents in the privilege logs, (3) and risking allowing non-privileged documents to be unfairly withheld. (4) As a result, privilege disputes have become a vexing legal problem. They await better solutions.

At the core of the disputes surrounding privileged documents is a simple trust problem: the privilege-claiming party holds secret documents that it is unwilling to show to the requesting party, who suspects the veracity of the privilege-claim. In other words, the privilege-claiming party wants to prove that the documents are indeed privileged without disclosing the documents' contents. This is, in fact, a classical problem that can be solved by a cryptographic concept called zero-knowledge proof.

Zero-knowledge proof has a seemingly contradictory definition: to be successful, a protocol needs to convince the verifier of the veracity of a statement without revealing the content supporting that statement. For example, if two children, Alice and Bob, want to see if they have received the same number of Halloween candies without showing each other their respective candy collections, they can use the following zero-knowledge proof implementation. Bob can label each of four locked boxes with different numbers. Only one box will be labeled with the number of candies that Bob has. He will keep the key to that box and will throw away the keys to all the other boxes. Alice will then slip identical pieces of paper into each box. If Alice sees a box labeled with the number of candies she holds, she will place a special mark on the paper she places in that box. If Bob then opens up the only box he has a key to, and sees the special mark, Alice and Bob will know they have the same number of candies; otherwise they will know they have different amounts of candies. (5) See Figure 1 for a visual representation of this scenario. Zero-knowledge proofs also serve a role in business and industry, such as acting as escrow agents in financial transactions, or calculating whether a salesperson has remitted appropriate taxes from her sales to be paid by a counterparty, without revealing the precise amount for which she was able to sell an item. (6)

Zero-knowledge proof is an active research area. Its applications in law have only recently begun to attract attention. Joshua Kroll contemplated applying zero-knowledge protocols to ensure that decision-makers or machine learning algorithms apply policies consistently across all decision subjects. …

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