Full-round Integral Cryptanalysis of the Lightweight Block Cipher INLEC

YU Bin; LIU Wenfen; CHEN Wen; GUO Ying; LU Yongcan; HUANG Yuehua

doi:10.11999/JEIT251131

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YU Bin, LIU Wenfen, CHEN Wen, GUO Ying, LU Yongcan, HUANG Yuehua. Full-round Integral Cryptanalysis of the Lightweight Block Cipher INLEC[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT251131

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YU Bin, LIU Wenfen, CHEN Wen, GUO Ying, LU Yongcan, HUANG Yuehua. Full-round Integral Cryptanalysis of the Lightweight Block Cipher INLEC[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT251131

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Full-round Integral Cryptanalysis of the Lightweight Block Cipher INLEC

doi: 10.11999/JEIT251131 cstr: 32379.14.JEIT251131

1.
School of Computer Science and Information Security, Guilin University of Electronic Technology, Guilin 541004, China
2.
Guangxi Key Laboratory of Cryptography and Information Security, Guilin University of Electronic Technology, Guilin 541004, China

Funds: The National Natural Science Foundation of China (61862011), Guangxi Natural Science Foundation (2019GXNSFGA245004), Innovation Project of Guangxi Graduate Education (YCSW2025374, YCSW2024351, YCBZ2024168), Henan Key Laboratory of Network Cryptography Technology (LNCT2025002)

Received Date: 2025-10-27
Accepted Date: 2026-04-15
Rev Recd Date: 2026-04-13

Available Online: 2026-04-30

Abstract

Abstract

Objective With the rapid development of telecommunication technology, Internet of Things (IoT) devices have been widely deployed in modern applications. However, their limited computing resources and energy supply create challenges for data privacy and security. To address these issues, Feng et al. proposed INLEC, a low-energy lightweight block cipher designed for resource-constrained IoT environments. The designers claimed that INLEC can resist differential, linear, impossible differential, and side-channel attacks. However, its security against integral cryptanalysis has not yet been evaluated. This paper presents a comprehensive full-round integral cryptanalysis of INLEC to assess its actual resistance to integral cryptanalysis. Methods The monomial prediction technique proposed by Hu et al. is used to construct a Mixed Integer Linear Programming (MILP) model for the monomial trails of INLEC. Based on this model, a 9-round integral distinguisher for INLEC is obtained. By further using the structural properties of the diffusion layer, the 9-round integral distinguisher is extended to a 10-round integral distinguisher by adding an initial round. This is the first 10-round integral distinguisher constructed for INLEC. To reduce the complexity of key recovery, a multi-key guessing method is proposed. Combined with the partial-sum technique, this method enables the first 14-round key recovery attack on INLEC. An integral cryptanalysis framework for the full-round INLEC cipher is therefore established. Results and Discussions The analysis shows that the 10-round integral distinguisher provides exploitable balanced bits for key recovery. Based on this distinguisher, the proposed 14-round key recovery attack achieves a data complexity of 2⁶³ chosen plaintexts and a time complexity of 2^89.843 14-round encryptions. These results indicate that the diffusion layer of INLEC does not fully eliminate integral properties within 10 rounds. The remaining structural properties can be used to support key recovery. This finding challenges the original security claims for INLEC and shows that integral properties should be considered when evaluating lightweight block ciphers for IoT applications. Conclusions This paper evaluates the resistance of the lightweight block cipher INLEC to integral cryptanalysis based on monomial prediction. A 9-round integral distinguisher is first constructed using a MILP model of monomial trails. The 9-round integral distinguisher is then extended to a 10-round integral distinguisher by exploiting the structural properties of the diffusion layer. A 14-round key recovery attack is further achieved by combining the partial-sum technique with the multi-key guessing method. The results show that INLEC has insufficient resistance to integral cryptanalysis and that its practical security may be lower than expected. Therefore, more rounds should be considered in the design of such ciphers to resist known integral attacks.
- Integral cryptanalysis,
- Monomial prediction,
- INLEC,
- Mixed Integer Linear Programming (MILP),
- Internet of things

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References(24)

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