• A node decomposition strategy is introduced to protect initial values of agents in cooperative–competitive multi-agent systems from honest-but-curious nodes and eavesdroppers without external algorithms.
• The proposed algorithm guarantees bipartite consensus while ensuring privacy, addressing negative interactions in signed networks.
• The approach avoids probabilistic limitations of differential privacy by using deterministic inter-node weight design.
• Two numerical simulations validate the effectiveness of the privacy-preserving bipartite consensus algorithm.