Beijing Zhongguancun Laboratory Tsinghua University Tsinghua University Tsinghua University Tsinghua University This document defines a "Signed MOAS Group", a Cryptographic Message Syntax (CMS) protected content type for use with the Resource Public Key Infrastructure (RPKI) to authenticate the collective announcement of IP prefixes by Multiple Origin Autonomous System (MOAS). The Signed MOAS Group mainly includes two parts: an IP prefix and a list of Autonomous Systems (ASes) authorized to announce the prefix. At least one of these ASes SHOULD be authorized to announce the prefix by the prefix owner through a Route Origin Authorization (ROA). The validation of a Signed MOAS Group confirms that the authorized ASes and other listed ASes have collectively agreed to announce the prefix, ensuring that the announcement is legitimate, accurate, and mutually authorized.