Attacks of Modified White-box AES Implementations

변형 화이트박스 고급 암호화 표준 구현 공격

White-box cryptography is a cryptographic implementation technique that protects the decryption key even if the attacker has access to the entire decryption process. It is a cryptographic technique applicable to digital rights management. Chow et al. proposed a white-box AES implementation adding extra data on AES. Their implementation was attacked by Billet et al. in time complexity 230. In this paper, we present new white-box AES implementations using different types of encodings. We generalize the previous attacks to this modified white-box AES implementations with various encodings. Through the analysis, we show that the attack complexity increases to 248 when 16-bit encoding functions are used, and further into 284 when the output of the 16-bit encoding function is used as an input of three S-boxes.