Obfuscating encrypted threshold signature algorithm and its applications in cloud computing

Current cloud computing causes serious restrictions to safeguarding users’ data privacy. Since users’ sensitive data is submitted in unencrypted forms to remote machines possessed and operated by untrusted service providers, users’ sensitive data may be leaked by service providers. Program obfuscation shows the unique advantages that it can provide for cloud computing. In this paper, we construct an encrypted threshold signature functionality, which can outsource the threshold signing rights of users to cloud server securely by applying obfuscation, while revealing no more sensitive information. The obfuscator is proven to satisfy the average case virtual black box property and existentially unforgeable under the decisional linear (DLIN) assumption and computational Diffie-Hellman (CDH) assumption in the standard model. Moreover, we implement our scheme using the Java pairing-based cryptography library on a laptop.

Cryptographic Software IP Protection without Compromising Performance or Timing Side-channel Leakage

Program obfuscation is a widely used cryptographic software intellectual property (IP) protection technique against reverse engineering attacks in embedded systems. However, very few works have studied the impact of combining various obfuscation techniques on the obscurity (difficulty of reverse engineering) and performance (execution time) of obfuscated programs. In this article, we propose a Genetic Algorithm (GA)-based framework that not only optimizes obscurity and performance of obfuscated cryptographic programs, but it also ensures very low timing side-channel leakage. Our proposed T iming S ide C hannel S ensitive P rogram O bfuscation O ptimization F ramework (TSC-SPOOF) determines the combination of obfuscation transformation functions that produce optimized obfuscated programs with preferred optimization parameters. In particular, TSC-SPOOF employs normalized compression distance (NCD) and channel capacity to measure obscurity and timing side-channel leakage, respectively. We also use RISC-V rocket core running on a Xilinx Zynq FPGA device as part of our framework to obtain realistic results. The experimental results clearly show that our proposed solution leads to cryptographic programs with lower execution time, higher obscurity, and lower timing side-channel leakage than unguided obfuscation.