Proposal and evaluation of a digital document protection scheme to specify whether the malicious entity is the sender or receiver

The digital signature scheme is one technology for proving that the signer of a digital document is genuine and guaranteeing the integrity of the digital document. A scheme using the digital signature of a Trusted Third Party (TTP) was standardized in ISO/IEC 15945 [1], but cannot specify whether the malicious entity is the sender or receiver when dishonest actions occur between the sender and receiver. An electronic notary system by the New Media Development Association and nonrepudiation mechanisms standardized in ISO/IEC 13888 were proposed as methods via a TTP to solve this problem. The processing load is critical when using TTP. However, these schemes do not take the processing load on the TTP into account and are therefore impractical in terms of processing performance. Hence, we propose a digital document protection scheme capable of specifying dishonest actions by either the sender or receiver, reducing the processing load on the TTP, and verifying the digital signature only when a problem has occurred. We further show that our proposed scheme is valid for digital documents such as electronic contracts of a few megabytes in size by comparing it with the above two schemes in terms of TTP transaction time. We also evaluate the data sizes retained by the TTP in our proposed scheme. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 88(8): 18–27, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20144