• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.1
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• pp.1-15
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• 2020

As differential computation analysis attack(DCA) which is context of side-channel analysis on white-box cryptography is proposed, masking white-box cryptography based on table encoding has been proposed by Lee et al. to counter DCA. Existing higher-order DCA for the masked white box cryptography did not consider the masking implementation structure based on table encoding, so it is impossible to apply this attack on the countermeasure suggested by Lee et al. In this paper, we propose a new higher-order DCA method that can be applied to the implementation of masking based on table encoding, and prove its effectiveness by finding secret key information of masking white-box cryptography suggested by Lee et al. in practice.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.273-287
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• 2016

White-box cryptography presented by Chow et al. is an obfuscation technique for protecting secret keys in software implementations even if an adversary has full access to the implementation of the encryption algorithm and full control over its execution platforms. Despite its practical importance, progress has not been substantial. In fact, it is repeated that as a proposal for a white-box implementation is reported, an attack of lower complexity is soon announced. This is mainly because most cryptanalytic methods target specific implementations, and there is no general attack tool for white-box cryptography. In this paper, we present an analytic toolbox on white-box implementations of the Chow et al.'s style using lookup tables. According to our toolbox, for a substitution-linear transformation cipher on n bits with S-boxes on m bits, the complexity for recovering the $$O\((3n/max(m_Q,m))2^{3max(m_Q,m)}+2min\{(n/m)L^{m+3}2^{2m},\;(n/m)L^32^{3m}+n{\log}L{\cdot}2^{L/2}\}\)$$, where $m_Q$ is the input size of nonlinear encodings,$m_A$ is the minimized block size of linear encodings, and $L=lcm(m_A,m_Q)$. As a result, a white-box implementation in the Chow et al.'s framework has complexity at most $O\(min\{(2^{2m}/m)n^{m+4},\;n{\log}n{\cdot}2^{n/2}\}\)$ which is much less than $2^n$. To overcome this, we introduce an idea that obfuscates two advanced encryption standard (AES)-128 ciphers at once with input/output encoding on 256 bits. To reduce storage, we use a sparse unsplit input encoding. As a result, our white-box AES implementation has up to 110-bit security against our toolbox, close to that of the original cipher. More generally, we may consider a white-box implementation of the t parallel encryption of AES to increase security.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.627-628
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• 2010

S. Chow proposes white-box cryptography mechanism of AES algorithm(WBC-AES) in 2002. WBC mechanism is implementation method which is resistant to white-box attack. We describe the WBC-AES and contents protection method using it.

• Smart Media Journal
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• v.12 no.9
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• pp.9-18
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• 2023

Black box cryptography is a cryptographic scheme based on a hardware encryption device, operating under the assumption that the device and the user can be trusted. However, with the increasing use of cryptographic algorithms on unreliable open platforms, the threats to black box cryptography systems have become even more significant. As a consequence, white box cryptography have been proposed to securely operate cryptographic algorithms on open platforms by hiding encryption keys during the encryption process, making it difficult for attackers to extract the keys. However, unlike traditional cryptography, white box-based encryption lacks established specifications, making challenging verify its structural security. To promote the safer utilization of white box cryptography, CHES organizes The WhibOx Contest periodically, which conducts safety analyses of various white box cryptographic techniques. Among these, the Differential Computation Analysis (DCA) attack proposed by Bos in 2016 is widely utilized in safety analyses and represents a powerful attack technique against robust white box block ciphers. Therefore, this paper analyzes the research trends in white box block ciphers and provides a summary of DCA attacks and relevant countermeasures. adhering to the format of a research paper.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.2
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• pp.115-123
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• 2019

White-box cryptography is an implementation technique in order to protect secret keys of cryptographic algorithms in the white-box attack model, which is the setting that an adversary has full access to the implementation of the cryptographic algorithm and full control over their execution. This concept was introduced in 2002 by Chow et al., and since then, there have been many proposals for secure implementations. While there have been many approaches to construct a secure white-box implementation for the ciphers with SPN structures, there was no notable result about the white-box implementation for the block ciphers with Feistel structure after white-box DES implementation was broken. In this paper, we propose a secure white-box implementation for a block cipher SEED with Feistel structure, which can prevent the previous known attacks for white-box implementations. Our proposal is simple and practical: it is performed by only 3,376 table lookups during each execution and the total size of tables is 762.5 KB.

• Journal of Digital Convergence
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• v.13 no.10
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• pp.343-351
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• 2015

With the diverse services of the current M2M environment being expanded to the organizations, the corporations, and the daily lives, the possibility of the occurrence of the vulnerabilities of the security of the related technologies have become an issue. In order to solve such a problem of the vulnerability of the security, this thesis proposes the technique for applying the cryptography algorithm for the protection of the device key of the M2M environment. The proposed technique was based on the elliptic curve cryptography Through the key exchange and the signature exchange in the beginning, the security session was created. And the white box cipher was applied to the encryption that creates the white box table using the security session key. Application results cipher algorithm, Elliptic Curve Cryptography provides a lightweight mutual authentication, a session key for protecting the communication session and a conventional white-box cipher algorithm and was guaranteed the session key used to encrypt protected in different ways. The proposed protocol has secure advantages against Data modulation and exposure, MITM(Man-in-the-middle attack), Data forgery and Manipulation attack.

• ETRI Journal
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• v.37 no.5
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• pp.1012-1022
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• 2015

Conventional cryptographic algorithms are not sufficient to protect secret keys and data in white-box environments, where an attacker has full visibility and control over an executing software code. For this reason, cryptographic algorithms have been redesigned to be resistant to white-box attacks. The first white-box AES (WB-AES) implementation was thought to provide reliable security in that all brute force attacks are infeasible even in white-box environments; however, this proved not to be the case. In particular, Billet and others presented a cryptanalysis of WB-AES with 230 time complexity, and Michiels and others generalized it for all substitution-linear transformation ciphers. Recently, a collision-based cryptanalysis was also reported. In this paper, we revisit Chow and others's first WB-AES implementation and present a conditional re-encoding method for cryptanalysis protection. The experimental results show that there is approximately a 57% increase in the memory requirement and a 20% increase in execution speed.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.5
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• pp.751-763
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• 2022

With the recent increase in spending growth in the IoT sector worldwide, the importance of lightweight block ciphers to encrypt them is also increasing. The lightweight block cipher PIPO algorithm proposed in ICISC 2020 is an SPN-structured cipher using an unbalanced bridge structure. The white box attack model refers to a state in which an attacker may know the intermediate value of the encryption operation. As a technique to cope with this, Chow et al. proposed a white box implementation technique and applied it to DES and AES in 2002. In this paper, we propose a white box PIPO applying a white box implementation to a lightweight block cipher PIPO algorithm. In the white box PIPO, the size of the table decreased by about 5.8 times and the calculation time decreased by about 17 times compared to the white box AES proposed by Chow and others. In addition, white box PIPO was used for mobile security products, and experimental results for each test case according to the scope of application are presented.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1382-1391
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• 2022

White-box cryptography can respond to white-box attacks that can access and modify memory by safely hiding keys in the lookup table. However, because the size of lookup tables is large and the speed of encryption is slow, it is difficult to apply them to devices that require real-time while having limited resources, such as IoT(Internet of Things) devices. In this work, we propose a scheme for collecting short-length plaintexts and processing them at once, utilizing the characteristics that white-box ciphers process encryption on a lookup table size basis. As a result of comparing the proposed method, assuming that the table sizes of the Chow and XiaoLai schemes were 720KB(Kilobytes) and 18,000KB, respectively, memory usage reduced by about 29.9% and 1.24% on average in the Chow and XiaoLai schemes. The latency was decreased by about 3.36% and about 2.6% on average in the Chow and XiaoLai schemes, respectively, at a Traffic Load Rate of 15 Mbps(Mega bit per second) or higher.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.3
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• pp.363-374
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• 2023

A white-box environment refers to a situation where the internal information of an algorithm is disclosed. The AES white-box encryption was first announced in 2002, and in 2016, a side-channel analysis for white-box encryption called Differential Computation Analysis (DCA) was proposed. DCA analysis is a powerful side-channel attack technique that uses the memory information of white-box encryption as side-channel information to find the key. Although various countermeasure studies against DCA have been published domestically and internationally, there were no evaluated or analyzed results from experiments applying the hiding technique using dummy operations to DCA analysis. Therefore, in this paper, we insert LU T-shaped dummy operations into the WBC-AES algorithm proposed by S. Chow in 2002 and quantitatively evaluate the degree of change in DCA analysis response depending on the size of the dummy. Compared to the DCA analysis proposed in 2016, which recovers a total of 16 bytes of the key, the countermeasure proposed in this paper was unable to recover up to 11 bytes of the key as the size of the dummy decreased, resulting in a maximum decrease in attack performance of about 68.8%, which is about 31.2% lower than the existing attack performance. The countermeasure proposed in this paper confirms that the attack performance significantly decreases as smaller dummy sizes are inserted and can be applied in various fields.