• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1261-1269
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• 2017

Feistel Networks are one of the most well-known schemes to design block ciphers. Generalized Feistel Networks are used to construct only block ciphers but also hash functions. Many generic attacks on Feistel schemes have been studied. Among these attacks, recently proposed meet-in-the-middle attacks are one of the most effective attacks. In this paper, we analyze the security of meet-in-the-middle attacks on generalized Feistel Networks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.3
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• pp.467-476
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• 2017

In this paper, we analyze Generalized Feistel Network(GFN) Type I, Type II, Type III that round function use SP update function, secret S-box and $k{\times}k$ MDS matirx. In this case an attacker has no advantage about S-box. For each type of GFN, we analyze and restore secret S-box in 9, 6, 6 round using the basis of integral cryptanalysis with chosen plaintext attack. Also we restore secret S-box in 16 round of GFN Type I with chosen ciphertext attack. In conclusion, we need $2^{2m}$ data complexity and ${\frac{2^{3m}}{32k}},{\frac{2^{3m}}{24k}},{\frac{2^{3m}}{36k}}$ time complexity to restore m bit secret S-box in GFN Type I, Type II, Type III.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.3421-3437
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• 2018

With the enlargement of wireless technology, vehicular ad-hoc networks (VANETs) are rising as a hopeful way to realize smart cities and address a lot of vital transportation problems such as road security, convenience, and efficiency. To achieve data confidentiality, integrity and authentication applying lightweight cryptosystems is widely recognized as a rather efficient approach for the VANETs. The Khudra cipher is such a lightweight cryptosystem with a typical Generalized Feistel Network, and supports 80-bit secret key. Up to now, little research of fault analysis has been devoted to attacking Khudra. On the basis of the single nibble-oriented fault model, we propose a differential fault analysis on Khudra. The attack can recover its 80-bit secret key by introducing only 2 faults. The results in this study will provides vital references for the security evaluations of other lightweight ciphers in the VANETs.