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DOI 10.34229/KCA2522-9664.26.3.13
UDC 004.056.55

O. Bespalov
G.E. Pukhov Institute for Modelling in Energy Engineering, National Academy of Sciences
of Ukraine, alexb5dh@gmail.com


CONSTRUCTING A CCA-SECURE MODIFICATION OF THE ALGORITHM
SPECIFIED IN DSTU 9041:2020

Abstract. This work presents a modification of the algorithm specified in DSTU 9041:2020 that is secure against both IND-CCA attacks and small-subgroup attacks, and is consistent with the existing National Standards of Ukraine. The Ukrainian State Standard DSTU 9041:2020, adopted in 2020, specifies a hybrid encryption algorithm. As shown in previous studies, it is secure against attacks aimed at recovering the key and the message, and it also provides IND-CPA security. However, it has also been demonstrated that it is not IND-CCA secure and is not secure against small-subgroup attacks. The present work remedies this shortcoming by constructing a modification of the algorithm that is secure against the aforementioned attacks.

Keywords: DSTU 9041, twisted Edwards curves, hybrid encryption, IND-CPA, IND-CCA, DDHP, small subgroups attacks.


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