Cryptology ePrint Archive: Report 2020/199

Improvement on a Masked White-box Cryptographic Implementation

Seungkwang Lee and Myungchul Kim

Abstract: White-box cryptography is a software technique to protect secret keys of cryptographic algorithms from attackers who have access to memory. By adapting techniques of differential power analysis to computation traces consisting of runtime information, Differential Computation Analysis (DCA) has recovered the secret keys from white-box cryptographic implementations. In order to thwart DCA, a masked white-box implementation has been suggested. However, each byte of the round output was not masked and just permuted by byte encodings. This is the main reason behind the success of DCA variants on the masked white-box implementation. In this paper, we improve the masked white-box cryptographic implementation in such a way to protect against DCA variants by obfuscating the round output with random masks. Specifically, we implement a white-box AES implementation applying masking techniques to the key-dependent intermediate value and the several outer-round outputs. Our analysis and experimental results show that the proposed method can protect against DCA variants including DCA with a 2-byte key guess, collision and bucketing attacks. This work requires approximately 3.7 times the table size and 0.7 times the number of lookups compared to the previous masked WB-AES implementation.

Category / Keywords: secret-key cryptography / white-box cryptography, masking, DCA, collision attack, bucketing attack, countermeasure

Date: received 17 Feb 2020, last revised 1 Mar 2020

Contact author: skwang at etri re kr,mck@kaist ac kr

Available format(s): PDF | BibTeX Citation

Version: 20200302:060433 (All versions of this report)

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