Cryptology ePrint Archive: Report 2021/1252

Complete Practical Side-Channel-Assisted Reverse Engineering of AES-Like Ciphers

Andrea Caforio and Fatih Balli and Subhadeep Banik

Abstract: Public knowledge about the structure of a cryptographic system is a standard assumption in the literature and algorithms are expected to guarantee security in a setting where only the encryption key is kept secret. Nevertheless, undisclosed proprietary cryptographic algorithms still find widespread use in applications both in the civil and military domains. Even though side-channel-based reverse engineering attacks that recover the hidden components of custom cryptosystems have been demonstrated for a wide range of constructions, the complete and practical reverse engineering of AES-128-like ciphers remains unattempted. In this work, we close this gap and propose the first practical reverse engineering of AES-128-like custom ciphers, i.e., algorithms that deploy undisclosed SubBytes, ShiftRows and MixColumns functions. By performing a side-channel-assisted differential power analysis, we show that the amount of traces required to fully recover the undisclosed components are relatively small, hence the possibility of a side-channel attack remains as a practical threat. The results apply to both 8-bit and 32-bit architectures and were validated on two common microcontroller platforms.

Category / Keywords: implementation / side-channel, DPA, reverse engineering, AES

Original Publication (in the same form): CARDIS-2021

Date: received 20 Sep 2021

Contact author: andrea caforio at epfl ch, fatih balli at csem ch, subhadeep banik at epfl ch

Available format(s): PDF | BibTeX Citation

Version: 20210920:142233 (All versions of this report)

Short URL: ia.cr/2021/1252


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