トランザクションの本人性を確認できる分散台帳技術の提案
Abstract
中央集権的組織に依存せずに仮想通貨やスマートコントラクトを実現する分散台帳技術が近年注目されている．分散台帳技術が今後安全かつ信頼できる社会基盤として普及するためには，取引の健全性，クレデンシャルの非中央集権的管理，承認権限の独占困難性，という3つの特徴を備えることが必要となる．しかしながら，現実に運用されている分散台帳ではこれらの特徴すべてを備えるものはなく，安全かつ信頼できる台帳管理を行うことは依然として困難であった．そこで我々は，これらの特徴をすべて備える基盤として，ユーザと不可分な秘密情報をトラストアンカとしてトランザクションの生成・承認を行うHuman Trusted Distributed Ledger（HTDL）を提案し，その要件を整理した．さらに，生体情報を秘密鍵として用いて署名生成を行うFuzzy signatureと，有向非循環グラフに基づき合意形成を行う方式を活用した，HTDLの構成方法を提案し，その構成がHTDLの要件を満たすことを示した．
Distributed ledger technology that realizes cryptocurrency and smart contract without depending on centralized organizations has received attention in recent years. In order for the distributed ledger technology to become popular as a secure and reliable social infrastructure in the future, it is necessary to have three characteristics: transaction soundness, decentralized credential management, and distributed authority. However, any practically operated distributed ledger do not have these three characteristics, and it is still difficult to manage secure and reliable ledgers without a trusted third party. Therefore, for satisfying the characteristics, we propose Human Trusted Distributed Ledger (HTDL), which creates and approves transactions with secret information that is indivisible to users. Moreover, we define the HTDL’s requirements for realizing secure and reliable distributed ledger. For the practical construction of the HTDL, we propose a HTDL construction method which utilizes fuzzy signature which can generate a digital signature from user’s biometric feature and a consensus method based on a directed acyclic graph, and show that the construction meets HTDL’s requirements.