White-box Implementation Research Articles

A White-box Implementation of SEED

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.

White-Box Implementation of Shamir’s Identity-Based Signature Scheme

Digital signature schemes have been extensively studied in the literature, where a large number of such schemes with different properties have been designed for different applications. For example, identity-based signature (IBS) schemes can efficiently map a user’s digital public key to his/her real-world identity (e.g., e-mail address). However, existing implementations of IBS schemes are not generally designed for white-box security (WBS), particularly concerning the protection of the private key when special attackers have full access to the execution environment. Therefore, in this paper, we propose the first white-box implementation for the classical Shamir’s IBS scheme. The basic idea is to utilize a mathematical transformation for embedding private key into some special tables, such that the original private key could be “invisible” during the execution process. We then analyze the security requirements achieved in our implementation, including the conventional black-box security under the random oracle model and WBS (e.g., key recovery attack resilience). This is the first IBS scheme implementation that satisfies WBS. It is also shown from the simulation that the implementation incurs a constant computational cost, which is realistic in deployments where a high security level is required.

How to reveal the secrets of an obscure white-box implementation

White-box cryptography (WBC) protects key extraction from software implementations of cryptographic primitives. Many academic works have been done achieving partial results toward WBC, but a complete solution has not been found yet by the cryptography community. As a result, the industry can only on proprietary and non-publicly scrutinized white-box implementations. It is therefore of interest to investigate the obtainable resistance of an AES implementation to thwart a white-box adversary in this paradigm. To this purpose, the ECRYPT CSA project has organized the WhibOx contest as the catch the flag challenge of CHES 2017. Researchers and engineers were invited to participate either as designers by submitting the source code of an AES-128 white-box implementation with a freely chosen key, or as breakers by trying to extract the hard-coded keys in the submissions. The participants were not expected to disclose their identities or the underlying designing/attacking techniques. In the end, 94 submitted challenges were all broken, and only 13 of them held more than one day. The strongest (in terms of surviving time) implementation survived for 28 days (which is more than twice as much as the second one). It was only broken by the authors of the present paper with reverse engineering and algebraic analysis. In this paper, we give a detailed description of the different steps of our cryptanalysis. We then generalize it to an attack methodology to break further obscure white-box implementations. In particular, we formalize and generalize the linear decoding analysis that we use to extract the key from the encoded intermediate variables of the target challenge.

White Box Implementations Using Non-Commutative Cryptography.

In this paper, we present a method to create a safe arithmetic that can be used to obfuscate implementations that require operations over commutative groups. The method is based on the structure of the endomorphisms of certain extensions of the original commutative group. The endomorphisms of a commutative group are non-commutative (in general), thus we can use a non-commutative group to emulate the arithmetic of a commutative one. The techniques presented in this paper are very flexible and the programmer has a wide variety of options to obfuscate the algorithms. The system can be parameterized using conjugations, thus it is possible to generate a different arithmetic for each instance of the program with a change in the security parameters, even in cases in which this number is huge (for example, in IoT applications). The security of this method is based not only on the difficulty of the conjugacy search problem (in a harder version because only partial information about the groups is known by the attacker), but also in a number of extra options that can be chosen by the programmer. The paper explains the general method, analyzes its algebraic properties and provides detailed examples based on the vector spaces over and XOR operators.

Analysis and Improvement of Differential Computation Attacks against Internally-Encoded White-Box Implementations

White-box cryptography is the last security barrier for a cryptographic software implementation deployed in an untrusted environment. The principle of internal encodings is a commonly used white-box technique to protect block cipher implementations. It consists in representing an implementation as a network of look-up tables which are then encoded using randomly generated bijections (the internal encodings). When this approach is implemented based on nibble (i.e. 4-bit wide) encodings, the protected implementation has been shown to be vulnerable to differential computation analysis (DCA). The latter is essentially an adaptation of differential power analysis techniques to computation traces consisting of runtime information, e.g., memory accesses, of the target software. In order to thwart DCA, it has then been suggested to use wider encodings, and in particular byte encodings, at least to protect the outer rounds of the block cipher which are the prime targets of DCA.In this work, we provide an in-depth analysis of when and why DCA works. We pinpoint the properties of the target variables and the encodings that make the attack (in)feasible. In particular, we show that DCA can break encodings wider than 4-bit, such as byte encodings. Additionally, we propose new DCA-like attacks inspired from side-channel analysis techniques. Specifically, we describe a collision attack particularly effective against the internal encoding countermeasure. We also investigate mutual information analysis (MIA) which naturally applies in this context. Compared to the original DCA, these attacks are also passive and they require very limited knowledge of the attacked implementation, but they achieve significant improvements in terms of trace complexity. All the analyses of our work are experimentally backed up with various attack simulation results. We also verified the practicability of our analyses and attack techniques against a publicly available white-box AES implementation protected with byte encodings –which DCA has failed to break before– and against a “masked” white-box AES implementation –which intends to resist DCA.

White-Box Cryptography: Don’t Forget About Grey-Box Attacks

Despite the fact that all current scientific white-box approaches of standardized cryptographic primitives have been publicly broken, these attacks require knowledge of the internal data representation used by the implementation. In practice, the level of implementation knowledge required is only attainable through significant reverse-engineering efforts. In this paper, we describe new approaches to assess the security of white-box implementations which require neither knowledge about the look-up tables used nor expensive reverse-engineering efforts. We introduce the differential computation analysis (DCA) attack which is the software counterpart of the differential power analysis attack as applied by the cryptographic hardware community. Similarly, the differential fault analysis (DFA) attack is the software counterpart of fault injection attacks on cryptographic hardware. For DCA, we developed plugins to widely available dynamic binary instrumentation (DBI) frameworks to produce software execution traces which contain information about the memory addresses being accessed. For the DFA attack, we developed modified emulators and plugins for DBI frameworks that allow injecting faults at selected moments within the execution of the encryption or decryption process as well as a framework to automate static fault injection. To illustrate the effectiveness, we show how DCA and DFA can extract the secret key from numerous publicly available non-commercial white-box implementations of standardized cryptographic algorithms. These approaches allow one to extract the secret key material from white-box implementations significantly faster and without specific knowledge of the white-box design in an automated or semi-automated manner.

A Masked White-Box Cryptographic Implementation for Protecting Against Differential Computation Analysis

Recently, gray-box attacks on white-box cryptographic implementations have succeeded. These attacks are more efficient than white-box attacks because they can be performed without detailed knowledge of the target implementation. The success of the gray-box attack is reportedly due to the unbalanced encodings used to generate the white-box lookup table. In this paper, we propose a method to protect the gray-box attack against white-box implementations. The basic idea is to apply the masking technique before encoding intermediate values during the white-box lookup table generation. Because we do not require any random source in runtime, it is possible to perform efficient encryption and decryption using our method. The security and performance analysis shows that the proposed method can be a reliable and efficient countermeasure.

On Recovering Affine Encodings in White-Box Implementations

Ever since the first candidate white-box implementations by Chow et al. in 2002, producing a secure white-box implementation of AES has remained an enduring challenge. Following the footsteps of the original proposal by Chow et al., other constructions were later built around the same framework. In this framework, the round function of the cipher is “encoded” by composing it with non-linear and affine layers known as encodings. However, all such attempts were broken by a series of increasingly efficient attacks that are able to peel off these encodings, eventually uncovering the underlying round function, and with it the secret key.These attacks, however, were generally ad-hoc and did not enjoy a wide applicability. As our main contribution, we propose a generic and efficient algorithm to recover affine encodings, for any Substitution-Permutation-Network (SPN) cipher, such as AES, and any form of affine encoding. For AES parameters, namely 128-bit blocks split into 16 parallel 8-bit S-boxes, affine encodings are recovered with a time complexity estimated at 232 basic operations, independently of how the encodings are built. This algorithm is directly applicable to a large class of schemes. We illustrate this on a recent proposal due to Baek, Cheon and Hong, which was not previously analyzed. While Baek et al. evaluate the security of their scheme to 110 bits, a direct application of our generic algorithm is able to break the scheme with an estimated time complexity of only 235 basic operations.As a second contribution, we show a different approach to cryptanalyzing the Baek et al. scheme, which reduces the analysis to a standalone combinatorial problem, ultimately achieving key recovery in time complexity 231. We also provide an implementation of the attack, which is able to recover the secret key in about 12 seconds on a standard desktop computer.

Protect white‐box AES to resist table composition attacks

White-box cryptography protects cryptographic software in a white-box attack context (WBAC), where the dynamic execution of the cryptographic software is under full control of an adversary. Protecting AES in the white-box setting attracted many scientists and engineers, and several solutions emerged. However, almost all these solutions have been badly broken by various efficient white-box attacks, which target compositions of key-embedding lookup tables. In 2014, Luo, Lai, and You proposed a new WBAC-oriented AES implementation, and claimed that their implementation is secure against both Billet et al. 's attack and De Mulder et al. 's attack. In this study, based on the existing table-composition-targeting cryptanalysis techniques, the authors show that the secret key of the Luo-Lai-You (LLY) implementation can be recovered with a time complexity of about 2 44 . Furthermore, the authors propose a new white-box AES implementation based on table lookups, which is shown to be resistant against the existing table-composition-targeting white-box attacks. The authors, key-embedding tables are obfuscated with large affine mappings, which cannot be cancelled out by table compositions of the existing cryptanalysis techniques. Although their implementation requires twice as much memory as the LLY WBAES to store the tables, its speed is about 63 times of the latter.

Towards practical white-box lightweight block cipher implementations for IoTs

According to the Kerckhoffs’s principle, the security of a system should be only depended on the security of its secret key. To build the trusted computing base, Secure Element (SE) and Trusted Execution Environment (TEE) have been proposed for secure computing and authentication. But users still need to believe that SE and TEE-supported hardware will not be evil or intruded. In order to totally remove the dependence of extra hardware, white-box cryptography was introduced by Chow et al. (2002) which gives a software solution for AES implementations in an extremely hostile environment. After Chow et al.’s seminal paper, many white-box implementations were proposed on different block ciphers. In IoTs applications, SE and TEE might have the practical issues if the implementation costs are constrained. In this paper, we first discuss the practical issues that relate to white-box block cipher implementations from lightweight block ciphers. Furthermore, we give the white-box implementations of KLEIN, Present and LBlock as the typical candidates that represent the Substitution-Permutation Network (SPN) and Feistel structures. Finally the performance and the costs are compared with the white-box AES implementation. The comparison shows that white-box implementations are not only related to block and key lengths, but also the structure of the cipher and its white-box implementation methodology strongly affect the implementation costs.

White-box Implementation to Advantage DRM

Digital Rights Management (DRM) is a popular approach for secure content distribution. Typically, DRM encrypts the content before delivers it. Most DRM applications use secure algorithms to protect content. However, executing these algorithms in an insecure environment may allow adversaries to compromise system and obtain the key. To withstand such attack, algorithm implementation is modified in such a way to make the implementation unintelligible, namely obfuscation approach. White-box cryptography (WBC) is an obfuscation technique intended to protect secret keys from being disclosed in a software implementation using a fully transparent methodology. This mechanism is appropriate for DRM applications and able to enhance security for content provider. However, DRM is required to provide a balanced protection for content provider and users. We construct a protocol on implementing WBC to improve DRM system; The system does not only provide security for content provider, but also preserves privacy for users.

White-box Implementation to Advantage DRM

<p class='IJASEITAbtract'>Digital Rights Management (DRM) is a popular approach for secure content distribution. Typically, DRM encrypts the content before delivers it. Most DRM applications use secure algorithms to protect content. However, executing these algorithms in an insecure environment may allow adversaries to compromise system and obtain the key. To withstand such attack, algorithm implementation is modified in such a way to make the implementation unintelligible, namely obfuscation approach. White-box cryptography (WBC) is an obfuscation technique intended to protect secret keys from being disclosed in a software implementation using a fully transparent methodology. This mechanism is appropriate for DRM applications and able to enhance security for content provider. However, DRM is required to provide a balanced protection for content provider and users. We construct a protocol on implementing WBC to improve DRM system; The system does not only provide security for content provider, but also preserves privacy for users.

A white-box AES-like implementation based on key-dependent substitution-linear transformations

It is becoming increasingly common to deploy cryptographic algorithms within software applications which are executed in untrusted environments owned and controlled by a possibly malicious party. White-box cryptography aims to protect the secret key in such an environment. Chow et al. developed a white-box AES implementation in 2002 by hiding secret keys into lookup tables. Afterwards, some improvements were proposed. However, all the published schemes have been shown to be insecure. AES was originally designed without consideration of execution in a white-box attack context. Because of the fixed confusion and diffusion operations, it is easy to break AES’s white-box version. In this paper, we propose an AES-like cipher by replacing AES’s S-boxes and MixColumn matrices with key-dependent components while keeping their good cryptographic properties. We show that the white-box implementation of our AES-like cipher can resist current known attacks.

Analysis of Software Countermeasures for Whitebox Encryption

Whitebox cryptography aims to ensure the security of cryptographic algorithms in the whitebox model where the adversary has full access to the execution environment. To attain security in this setting is a challenging problem: Indeed, all published whitebox implementations of standard symmetric-key algorithms such as AES to date have been practically broken. However, as far as we know, no whitebox implementation in real-world products has suffered from a key recovery attack. This is due to the fact that commercial products deploy additional software protection mechanisms on top of the whitebox implementation. This makes practical attacks much less feasible in real-world applications. There are numerous software protection mechanisms which protect against standard whitebox attacks. One such technique is control flow obfuscation which randomizes the order of table lookups for each execution of the whitebox encryption module. Another technique is randomizing the locations of the various Look up tables (LUTs) in the memory address space. In this paper we investigate the effectiveness of these countermeasures against two attack paradigms. The first known as Differential Computational Analysis (DCA) attack was developed by Bos, Hubain, Michiels and Teuwen in CHES 2016. The attack passively collects software execution traces for several plaintext encryptions and uses the collected data to perform an analysis similar to the well known differential power attacks (DPA) to recover the secret key. Since the software execution traces contain time demarcated physical addresses of memory locations being read/written into, they essentially leak the values of the inputs to the various LUTs accessed during the whitebox encryption operation, which as it turns out leaks sufficient information to perform the power attack. We found that if in addition to control flow obfuscation, one were to randomize the locations of the LUTs in the memory, then it is very difficult to perform the DCA on the resultant system using such table inputs and extract the secret key in reasonable time. As an alternative, we investigate the version of the DCA attack which uses the outputs of the tables instead of the inputs to mount the power analysis attack. This modified DCA is able to extract the secret key from the flow obfuscated and location randomized versions of several whitebox binaries available in crypto literature. We develop another attack called the Zero Difference Enumeration (ZDE) attack. The attack records software traces for several pairs of strategically selected plaintexts and performs a simple statistical test on the effective difference of the traces to extract the secret key. We show that ZDE is able to recover the keys of whitebox systems. Finally we propose a new countermeasure for protecting whitebox binaries based on insertion of random delays which aims to make both the ZDE and DCA attackspractically difficult by adding random noise in the information leaked to the attacker.

Analysis of Software Countermeasures for Whitebox Encryption

Whitebox cryptography aims to ensure the security of cryptographic algorithms in the whitebox model where the adversary has full access to the execution environment. To attain security in this setting is a challenging problem: Indeed, all published whitebox implementations of standard symmetric-key algorithms such as AES to date have been practically broken. However, as far as we know, no whitebox implementation in real-world products has suffered from a key recovery attack. This is due to the fact that commercial products deploy additional software protection mechanisms on top of the whitebox implementation. This makes practical attacks much less feasible in real-world applications. There are numerous software protection mechanisms which protect against standard whitebox attacks. One such technique is control flow obfuscation which randomizes the order of table lookups for each execution of the whitebox encryption module. Another technique is randomizing the locations of the various Look up tables (LUTs) in the memory address space. In this paper we investigate the effectiveness of these countermeasures against two attack paradigms. The first known as Differential Computational Analysis (DCA) attack was developed by Bos, Hubain, Michiels and Teuwen in CHES 2016. The attack passively collects software execution traces for several plaintext encryptions and uses the collected data to perform an analysis similar to the well known differential power attacks (DPA) to recover the secret key. Since the software execution traces contain time demarcated physical addresses of memory locations being read/written into, they essentially leak the values of the inputs to the various LUTs accessed during the whitebox encryption operation, which as it turns out leaks sufficient information to perform the power attack. We found that if in addition to control flow obfuscation, one were to randomize the locations of the LUTs in the memory, then it is very difficult to perform the DCA on the resultant system using such table inputs and extract the secret key in reasonable time. As an alternative, we investigate the version of the DCA attack which uses the outputs of the tables instead of the inputs to mount the power analysis attack. This modified DCA is able to extract the secret key from the flow obfuscated and location randomized versions of several whitebox binaries available in crypto literature. We develop another attack called the Zero Difference Enumeration (ZDE) attack. The attack records software traces for several pairs of strategically selected plaintexts and performs a simple statistical test on the effective difference of the traces to extract the secret key. We show that ZDE is able to recover the keys of whitebox systems. Finally we propose a new countermeasure for protecting whitebox binaries based on insertion of random delays which aims to make both the ZDE and DCA attackspractically difficult by adding random noise in the information leaked to the attacker.

White-box AES implementation revisited

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 whitebox 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.

An AES-Like Cipher and Its White-Box Implementation

White-box cryptography aims at implementing a cipher to protect its key from being extracted in an untrusted environment, where the attacker has full access to the execution of the cryptographic software. In 2002, Chow proposed the original white-box implementation of AES. Afterwards, various white-box implementations were presented. However, they were all badly broken because of a weakness of the implemented cryptographic algorithms: every parameter of the cryptographic operations is fixed except the round keys. In this paper, we present an AES-like cipher based on key-dependent S-boxes. The new cipher is designed to meet the design criteria of AES and hence provides a security level comparable to AES to resist black-box attacks. Moreover, we present a white-box implementation for our AES-like cipher, which is sufficient to withstand existing white-box attacks.

Efficient Attack to White-Box SMS4 Implementation

PDF HTML阅读 XML下载 导出引用 引用提醒 对白盒SMS4实现的一种有效攻击 DOI: 10.3724/SP.J.1001.2013.04356 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(61073149) Efficient Attack to White-Box SMS4 Implementation Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:传统的密码模型都假设密码系统的运行终端和计算环境是可信任的,但是,随着攻击方式的发展,这样的模型显得越来越脆弱.而白盒攻击环境是指攻击者除了能够获得与传统密码模型同样的资源以外,还对密码系统的内部运行完全可见,并完全掌控执行环境.因此,能够抵抗白盒攻击的密码算法具有更高层次的安全意义.2009 年提出的SMS4 算法的白盒实现,其目标是在白盒攻击环境下能够防止SMS4 算法的密钥被恢复.在回顾已有研究的基础上,针对该SMS4 算法的白盒实现提出了一种有效的攻击,并详细解释了如何以低于247 的时间复杂度找出嵌入其中的轮密钥,说明了该白盒设计方法的不可靠性,并为设计安全的白盒实现提供了一种参考. Abstract:In traditional cryptographic model, it is assumed that the communication end points and computing environments of a cryptosystem are trusted. But this model becomes increasingly frailer with the development of the attack method. In the white-box attack model, the adversary can get not only access to the same resources as in the traditional cryptographic model but also total visibility of the internal implementation of the cryptosystem and full control over its execution environment, so it has the higher level of secure significance. The white-box SMS4 implementation, which was proposed in 2009, is aimed at protecting SMS4 operated in the white box context against key exposure. In this paper, based on the review of previous research, we propose an efficient attack and explain in detail how to extract the round key embedded in such a white box SMS4 implementation, with worst time complexity 247. As a result, we show that the white-box method is unreliable and provide reference for the secure white-box implementation. 参考文献 相似文献 引证文献

Opportunities in White-Box Cryptography

White-box cryptography is the discipline of implementing a cryptographic algorithm in software such that an adversary will have difficulty extracting the cryptographic key. This approach assumes that the adversary has full access to and full control over the implementation's execution. White-box implementations can provide good protection when combined with other security measures.