Improved Meet-in-the-Middle Attacks on Reduced-Round Kiasu-BC and Joltik-BC
COMPUTER JOURNAL(2019)
摘要
Kiasu-BC and Joltik-BC are internal tweakable block ciphers of authenticated encryption algorithms Kiasu and Joltik submitted to the CAESAR competition. Kiasu-BC is a 128-bit block cipher, of which tweak and key sizes are 64 and 128 bits, respectively. Joltik-BC-128 is a 64-bit lightweight block cipher supporting 128 bits tweakey. Its designers recommended the key and tweak sizes are both 64 bits. In this paper, we propose improved meet-in-the-middle attacks on 8-round Kiasu-BC, 9-round and 10-round Joltik-BC-128 by exploiting properties of their structures and using precomputation tables and the differential enumeration. For Kiasu-BC, we build a 5-round distinguisher to attack 8-round Kiasu-BC with 2(109) plaintext-tweaks, 2(112.8) encrytions and 2(92.91) blocks. Compared with previously best known cryptanalytic results on 8-round Kiasu-BC under chosen plaintext attacks, the data and time complexities are reduced by 2(7) and 2(3.2) times, respectively. For the recommended version of Joltik-BC-128, we construct a 6-round distinguisher to attack 9-round Joltik-BC-128 with 2(53) plaintext-tweaks, 2(56.6) encryptions and 2(52.91) blocks, respectively. Compared with previously best known results, the data and time complexities are reduced by 2(7) and 2(5.1) times, respectively. In addition, we present a 6.5-round distinguisher to attack 10-round Joltik-BC-128 with 2(53) plaintext-tweaks, 2(101.4) encryptions and 2(76.91) blocks.
更多查看译文
关键词
tweakable block ciphers,tweakey,Kiasu-BC,Joltik-BC,meet-in-the-middle attacks
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络