基於區塊鏈之數位鑑識證據監管鏈

數位鑑識實驗室在受理案件時，鑑識人員需使用有效的數位鑑識工具，依正確的數位證據監管鏈原則將證據擷取出來，如此才能確保該證據在法律訴訟過程中具備證據能力。然而現行的蒐證作業多以紙本表單紀錄證據資訊，包含：數位證據蒐集工作表、證據取得清單表以及證據監管鏈表，而撰寫、修改表單紀錄的工作相當耗費人力和物力，且移交過程也可能出錯。因此本論文針對證據監管鏈表建構出「區塊鏈數位鑑識證據監管鏈平台」系統雛形，利用以太坊區塊鏈的 ERC 721 代幣標準及 ECQV 隱含式憑證（Elliptic Curve Qu-Vanstone Implicit Certificates）的技術改善上述問題。本平台為每張證據監管鏈表發行一個 ERC 721 不可替換代幣，在鏈上紀錄其內容的異動及所有權的移轉，並採用 Clique PoA 共識機制同步各參加節點的資料，達到證據監管鏈表的完整性認證。此外，所有用戶在加入本聯盟鏈前須先向 CA 申請一張 ECQV 隱含式憑證做身份認證，而 ECQV 憑證的容量較小、金鑰安全強度強，適合放在區塊鏈上傳遞以做證據監管鏈表的簽驗章、加解密達到機敏性及不可否認性。

關鍵字

以太坊區塊鏈；數位鑑識；證據監管鏈；智能合約； ERC 721 代幣標準； PoA Clique 共識機制； ECQV 隱含式憑證

並列摘要

When a digital forensics library acceptes a case, the forensics staffs of the library need to collect the evidence by using legal forensics tools according to the proper principle of Digital Forensics Chain of Custody. In this way, we can make sure that the extracted evidence has the evidential effect during the litigation. However, currently the coollecting process is being recorded and modified in paper work including Digital evidence collection worksheet, Incoming Evidence Form, and Chain of Custody Form which requires lots of huam resources and is time consumin. Focusing on Chain of Custody Form, this thesis proposes a blockchain based digital forensics chain of custody. This platfrom, to some extent, solves the problems mentioned above. The building blocks and the core techniques we used here including the Ethereum blockchain and ECQV implicit certificates. In order to attain the data integrity, this platform release ERC 721 non-fungible token for each chain of custody form, recording all modificatory history of ownersship and context. In addition, it adopts the Clique PoA consensus to sync the data of all nodes on the chain. Furthermore, all the users need to apply for an ECQV certificate from CA to athenticate the identification before the participating consortium chain. The reasons why we use ECQV certificates are beacuse of its smaller size and more secure of keys comparing with traditional certificates. So that we can put it on the blockchain for transmission, leting users to sign, verify, encrypt and decrypt the chain of custody for the purpose of achieving the data confidentiality and non-repudiation.