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

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

Available Online: 2026-04-30

Abstract

Abstract

Objective With the rapid advancement of telecommunication technology, Internet of Things (IoT) devices have become increasingly ubiquitous in modern applications. However, their limited computational capabilities and energy constraints present significant challenges for data privacy and security. To address these challenges, Feng et al. proposed INLEC, a low-energy lightweight block cipher tailored for resource-constrained IoT environments. While the designers claimed that INLEC is resistant to various forms of cryptanalysis—such as differential, linear, impossible differential, and side-channel attacks—its security against integral cryptanalysis has not yet been investigated. The objective of this paper is to conduct a comprehensive full-round integral analysis of the INLEC cipher to evaluate its actual resistance to this important cryptanalytic technique. Methods In this paper, the monomial prediction technique proposed by Hu et al. is utilized to construct a MILP model that characterizes the monomial trails of the INLEC block cipher. Through this model, a 9-round integral distinguisher for INLEC is successfully derived. Furthermore, by leveraging the structural properties of the diffusion layer used in INLEC, the distinguisher is extended to 10 rounds by incorporating an additional initial round. This constitutes the first construction of a 10-round integral distinguisher for INLEC. To further reduce the complexity of key recovery, a multi-key guessing method is proposed. When combined with the partial-sum technique, the first 14-round key recovery attack on INLEC is achieved. Consequently, an integral cryptanalysis framework applicable to the full-round INLEC cipher is established. Results and Discussions The experimental analysis reveals that the 10-round distinguisher provides an effective statistical bias that can be exploited for key recovery. Based on this distinguisher, the proposed 14-round attack achieves a data complexity of $ {2}^{63} $ and a time complexity equivalent to $ {2}^{89.843} $ 14-round encryptions. The attack demonstrates that INLEC’s diffusion layer does not achieve full state randomization within 10 rounds, leaving exploitable structural weaknesses in its internal transformation. These findings challenge the designers’ original security claims and highlight the importance of considering integral properties when assessing lightweight ciphers intended for IoT applications. Conclusions This paper presents a comprehensive evaluation of the resistance of the lightweight block cipher INLEC against integral cryptanalysis, based on the monomial prediction technique. The analysis shows that INLEC is insufficiently resistant to integral attacks, and that the proposed method poses a realistic threat in practical scenarios. These results highlight the need for more rounds in cipher design to defend against known integral cryptanalysis. Additionally, the diffusion layer should be designed to avoid weak algebraic structures, thereby improving resistance to 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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