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On the ineffectiveness of internal encodings - Revisiting the DCA attack on white-box cryptography
Publikationstyp
Conference Paper
Date Issued
2018-07
Sprache
English
Institut
First published in
Number in series
10892 LNSC
Start Page
103
End Page
120
Citation
International Conference on Applied Cryptography and Network Security (ACNS 2018)
Contribution to Conference
Publisher DOI
Scopus ID
The goal of white-box cryptography is to implement cryptographic algorithms securely in software in the presence of an adversary that has complete access to the software’s program code and execution environment. In particular, white-box cryptography needs to protect the embedded secret key from being extracted. Bos et al. (CHES 2016) introduced differential computational analysis (DCA), the first automated attack on white-box cryptography. The DCA attack performs a statistical analysis on execution traces. These traces contain information such as memory addresses or register values, that is collected via binary instrumentation tooling during the encryption process. The white-box implementations that were attacked by Bos et al., as well as white-box implementations that have been described in the literature, protect the embedded key by using internal encodings techniques introduced by Chow et al. (SAC 2002). Thereby, a combination of linear and non-liner nibble encodings is used to protect the secret key. In this paper we analyse the use of such internal encodings and prove rigorously that they are too weak to protect against DCA. We prove that the use of non-linear nibble encodings does not hide key dependent correlations, such that a DCA attack succeeds with high probability.
Subjects
Differential computational analysis
Mixing bijections
Software execution traces
White-box cryptography