Opacity Enforcement via Greedy Privately-and-Publicly Known Insertion Functions

• 成果类型: Article
• 署名作者: Liu, Rongjian; Lu, Jianquan; Liu, Yang; Yin, Xiang; Hadjicostis, Christoforos N.
• 署名单位: Chongqing Normal University; Southeast University - China; Southeast University - China; Zhejiang Normal University; Shanghai Jiao Tong University; University of Cyprus
• 刊物名称: IEEE TRANSACTIONS ON AUTOMATIC CONTROL
• ISSN/ISSBN: 0018-9286
• DOI: 10.1109/TAC.2023.3307791
• 发表日期: 2024
• 页码: 2500-2506
• 关键词: automata; observers; STANDARDS; mathematics; Complexity theory; Behavioral sciences; System recovery; Discrete event systems (DES); insertion mechanism; opacity enforcement; publicly known obfuscation

摘要

In this article, we investigate the enforcement of (current-state) opacity, an important information-flow security property, via insertion functions. An insertion function is an obfuscation mechanism that inserts fictitious events to the outputs in order to confuse the outside observer (intruder) such that the secret of the system is not revealed. In some situations, the secret may be revealed when the insertion mechanism is (or becomes) publicly known. This leads to the problem of synthesizing private-and-public enforcing (PP-enforcing) insertion functions in the sense that opacity is still enforced even when the mechanism is discovered or published by the designer. Existing works that have investigated this synthesis problem are either only sound or have limited applicability as we show in this work. For this reason, and more importantly, to better solve the synthesis problem, a new approach is proposed upon an improved greedy criterion. We show that the proposed algorithm is both sound and complete, and can be used to completely solve the synthesis problem for the PP-enforcing insertion function. With slight modifications of our algorithm, infinite-step opacity and K-step opacity can also be enforced under publicly-known insertion mechanisms.