In order to guarantee anonymity and untraceability of information, blind signature schemes are widely used in many specific communication scenarios, such as e-commerce, the electronic bidding, and so on. In this chapter, we propose a broadcast blind multi-signature scheme based on RSA, and the security of our scheme is proved under the RSA one-way problem in the random oracle model. Through the organic combination of multiple signatures and blind signatures, our proposed scheme enables multiple signers to complete a multi-signature with their own identity private keys, while avoiding the content of the message being known by signers. This method reduces the risk of information to be signed being leaked and tampered and realizes the balance of high efficiency and security in the process of multiple signing. Furthermore, our proposed scheme avoids the dependence on secure channels during the distribution of identity private keys, which reduces the communication cost of multi-signatures.