A designer of secure Electronic Data Interchange (EDI) or other emerging electronic commerce systems must consider an EDI-specific threat-repudiation of receipt-in addition to general security services such as authentication, confidentiality and integrity. We address this security issue by first examining the previous work done in this area, and then proposing a novel protocol to achieve non-repudiation of receipt. By using two simple ideas, a conditional signature and a public notice-board, the new protocol can achieve this security service in a simple but effective manner.