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SPEEDY is a family of ultra-lightweight block ciphers designed by Leander et al. at CHES 2021. There are three recommended variants denoted as SPEEDY-r-192 with . All of them support the 192-bit block and the 192-bit key. The main focus during its design is to ensure hardware-aware low latency, thus, whether it is designed to have enough security is worth to be studied. Recently, the full-round security of SPEEDY-7-192 is announced to be broken by Boura et al. at EUROCRYPT 2023 under the chosen-ciphertext setting, where a round-reduced attack on SPEEDY-6-192 is also proposed. However, no valid attack on SPEEDY-5-192 is given due to its more restricted security parameters. Up to now, the best key recovery attack on this variant only covers 3 rounds proposed by Rohit et al. at AFRICACRYPT 2022.

In this paper, we give three full-round attacks on SPEEDY-7-192. Using the divide-and …