In recent years, individuals have had a lot of opportunities to post information on the Internet, such as online shopping reviews and comments on online news. However, the number of malicious postings, such as fake reviews and disinformation in online media comments, continues to exist. Meanwhile, self-sovereign identity systems are becoming more widespread. In such systems, identity information, such as a name, the organization they belong to, and their qualifications, can be digitized and managed by themselves. In some identity systems, selective disclosure is possible. They can keep their name confidential and disclose only their occupation. In this paper, we propose a new information-sharing system that allows contributors who post information on the Internet to present part of their identity information to guarantee their authenticity, managed by self-sovereign identities, while preserving their privacy and preventing multi-posts. In the proposed system, viewers who view the posted information are able to distinguish reliable information based on the contributor’s identity. While contributors’ privacy must be protected, it should also be prevented that a single contributor can impersonate many other contributors for a particular piece of information by repeatedly using their identity information. Therefore, we propose a new method to prevent such multiple postings while preserving the privacy of the contributors.