In Internet electronic commerce, transaction costs including search and communication costs can be reduced, and detailed information about specific products and prices from diverse sellers can be provided to consumers, thereby improving transaction efficiency. On the other hand, unlike closed networks where several security safeguards are maintained, secure transactions are not guaranteed in Internet commerce due to its inherent characteristics as an open distributed network. In other words, to enhance the efficiency of Internet commerce, a secure payment system that provides confidential information transmission, message integrity, authentication between transaction parties, and payment settlement functions needs to be established. Therefore, this study investigates and analyzes six third-party payment systems that are currently being developed or operated, seeking answers to the following questions and discussing them: What payment systems currently exist, and how do they provide security services? What are the advantages and limitations of each payment system? What are the key factors to consider when designing a payment system? What trade-offs exist among these factors, and how should they be addressed?