HC-128 is an eSTREAM finalist and no practical attack on this cipher is known. We show that the knowledge of any one of the two internal state arrays of HC-128 along with the knowledge of 2048 keystream words is sufficient to construct the other state array completely in 242 time complexity. Though our analysis does not lead to any attack on HC-128, it reveals a structural insight into the cipher. In the process, we theoretically establish certain combinatorial properties of HC-128 keystream generation algorithm. Our work may be considered as the first step towards a possible state recovery of HC-128. We also suggest a modification to HC-128 that takes care of the recently known cryptanalytic results with little reduction in speed. © 2011 Springer-Verlag.
CITATION STYLE
Paul, G., Maitra, S., & Raizada, S. (2011). A theoretical analysis of the structure of HC-128. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 7038 LNCS, pp. 161–177). https://doi.org/10.1007/978-3-642-25141-2_11
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