Protecting Encrypted Signature Functions Against Intrusions on Computing Devices by Obfuscation

Digital signature schemes are widely used to protect information integrity in computer communications. However, conventional digital signature schemes are secure only in normal attack contexts. Technically, these schemes assume that the signing algorithm implementation is running in a perfectly secure platform protected from various kinds of attacks and intrusions. To complement existing studies, this paper studies how to securely generate identity-based signatures, key-insulated signatures, and fuzzy identity-based signatures in a more austere attack context, such as on a computing device that is potentially controlled by an attacker. We use program obfuscation for achieving a higher security level. Concretely, we give three specialized signature functions—encrypted identity-based signature, encrypted key-insulated signature, and encrypted fuzzy identity-based signature, and then propose an obfuscator for the three encrypted signature functions. The efficiency of the proposed obfuscator is theoretically analyzed, and the correctness and security are proved. Finally, we present experimental results that show the proposed scheme is efficient. As a result, the obfuscated implementations of these encrypted signature functions can be applied to many protocols and enhance their security.