COMBO: Pre-Training Representations of Binary Code Using Contrastive Learning

Compiled software is delivered as executable binary code. Developers write source code to express the software semantics, but the compiler converts it to a binary format that the CPU can directly execute. Therefore, binary code analysis is critical to applications in reverse engineering and computer security tasks where source code is not available. However, unlike source code and natural language that contain rich semantic information, binary code is typically difficult for human engineers to understand and analyze. While existing work uses AI models to assist source code analysis, few studies have considered binary code. In this paper, we propose a COntrastive learning Model for Binary cOde Analysis, or COMBO, that incorporates source code and comment information into binary code during representation learning. Specifically, we present three components in COMBO: (1) a primary contrastive learning method for cold-start pre-training, (2) a simplex interpolation method to incorporate source code, comments, and binary code, and (3) an intermediate representation learning algorithm to provide binary code embeddings. Finally, we evaluate the effectiveness of the pre-trained representations produced by COMBO using three indicative downstream tasks relating to binary code: algorithmic functionality classification, binary code similarity, and vulnerability detection. Our experimental results show that COMBO facilitates representation learning of binary code visualized by distribution analysis, and improves the performance on all three downstream tasks by 5.45% on average compared to state-of-the-art large-scale language representation models. To the best of our knowledge, COMBO is the first language representation model that incorporates source code, binary code, and comments into contrastive code representation learning and unifies multiple tasks for binary code analysis.