We propose a new and secure identity-based multi-signature scheme based on the Schnorr scheme. This is the first identity-based multi-signature system using the Schnorr signature scheme that is secure in the basic public-key architecture, facilitating key aggregation and public key validation via the identities of group members. The security of our suggested scheme is established in the random oracle model based on the discrete logarithm problem. Moreover, this approach is resilient to prevalent attacks, including key forgery, information modification, and replay attacks, by generating keys from user IDs and utilizing time stamps. Within the context of the document management system for Vietnamese organizations and businesses, we provide an explanation of how our new identity-based multi-signature scheme may be used to enhance both the system’s performance and its legitimacy. We provide an estimation of its performance and conduct a security analysis, including a comparison with the state of the art in multi-signature schemes.