## Cryptology ePrint Archive: Report 2014/987

Cryptanalysis of Full PRIDE Block Cipher

Yibin Dai and Shaozhen Chen

Abstract: PRIDE is a lightweight block ciphers designed by Albrecht et al., appears in CRYPTO 2014. The designers claim that the construction of linear layers is nicely in line with a bit-sliced implementation of the Sbox layer and security. In this paper, we find 8 2-round iterative related-key differential characteristics, which can be used to construct 18-round related-key differentials. Then, by discussing the function $g^{(1)}_r$, we also find 4 2-round iterative related-key differential characteristics with $\Delta g^{(1)}_r(k_{1,2})=0x80$ and 4 2-round iterative characteristics with $\Delta g^{(1)}_r(k_{1,2})=0x20$ which cause three weak-key classes. Based on the related-key differentials, we launch related-key differential attack on full PRIDE. The data and time complexity are $2^{39}$ chosen plaintexts and $2^{60}$ encryptions, respectively. Moreover, by using multi related-key differentials, we improve the cryptanalysis, which requires $2^{41.4}$ chosen plaintexts and $2^{44}$ encryptions, respectively. Finally, by using 17-round related-key differentials, the cryptanalysis requires $2^{34}$ plaintexts and $2^{53.7}$ encryptions. These are the first results on full PRIDE.

Category / Keywords: secret-key cryptography / Cryptanalysis; Block cipher