Circuits Systems and Signal Processing, Jan 9, 2005
We have proposed a chaotic cryptographic scheme based on iterating the logistic map and updating ... more We have proposed a chaotic cryptographic scheme based on iterating the logistic map and updating the look-up table dynamically. However, it has been broken recently. In this paper, the weaknesses of the original dynamic look-up table scheme are analyzed and a more secure chaotic encryption scheme based on this dynamic look-up table concept is proposed. Theoretical analysis indicates that the modified scheme can resist the reported attacks. Moreover, simulation results show that this encryption scheme leads to a flat ciphertext distribution.
Proceedings Icip International Conference on Image Processing, Feb 8, 2010
Motivated by the work of Uehara et al. [1], an improved method to recover DC coefficients from AC... more Motivated by the work of Uehara et al. [1], an improved method to recover DC coefficients from AC coefficients of DCT-transformed images is investigated in this work, which finds applications in cryptanalysis of selective multimedia encryption. The proposed under/over-flow rate minimization (FRM) method employs an optimization process to get a statistically more accurate estimation of unknown DC coefficients, thus achieving a better recovery performance. It was shown by experimental results based on 200 test images that the proposed DC recovery method significantly improves the quality of most recovered images in terms of the PSNR values and several state-of-the-art objective image quality assessment (IQA) metrics such as SSIM and MS-SSIM.
School of Electrical Engineering Computer Science Science Engineering Faculty, Dec 7, 2009
Recently a new human authentication scheme called PAS (predicate-based authentication service) wa... more Recently a new human authentication scheme called PAS (predicate-based authentication service) was proposed, which does not require the assistance of any supplementary device. The main security claim of PAS is to resist passive adversaries who can observe the whole authentication session between the human user and the remote server.
Unimodal maps have been broadly used as a base of new encryption strategies. Recently, a stream c... more Unimodal maps have been broadly used as a base of new encryption strategies. Recently, a stream cipher has been proposed in the literature, whose keystream is basically a symbolic sequence of the (one-parameter) logistic map or of the tent map. In the present work a thorough analysis of the keystream is made which reveals the existence of some serious security problems.
Iee Proceedings Vision Image and Signal Processing, Mar 9, 2006
Recently, a VoIP (voice over Internet protocol) technique with a new hierarchical data security p... more Recently, a VoIP (voice over Internet protocol) technique with a new hierarchical data security protection (HDSP) scheme was proposed by using a secret chaotic bit sequence. This paper points out some insecure properties of the HDSP scheme, and then uses them to develop known/chosen-plaintext attacks. The following main findings are: 1) given n known plaintexts, about (100 − 50 2 n ) percent of secret chaotic bits can be uniquely determined; 2) given only one specially-chosen plaintext, all secret chaotic bits can be uniquely derived; 3) the secret key can be derived with practically small computational complexity when only one plaintext is known (or chosen). These facts reveal that HDSP is very weak against known/chosen-plaintext attacks. Experiments are given to show the feasibility of the proposed attacks. Furthermore, it is also found that the security of HDSP against the brute-force attack is not practically strong. Finally, some countermeasures are discussed for enhancing the security of HDSP, and several basic principles are suggested for the design of a secure encryption scheme.
In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped ne... more In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped neural network (CNN) for encryption. The present paper analyzes the security of this chaotic cipher against chosen-plaintext attacks, and points out that this cipher can be broken by a chosen-plaintext attack. Experimental analyses are given to support the feasibility of the proposed attack.
In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped ne... more In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped neural network (CNN) for encryption. The present paper analyzes the security of this chaotic cipher against chosen-plaintext attacks, and points out that this cipher can be broken by a chosen-plaintext attack. Experimental analyses are given to support the feasibility of the proposed attack.
Recently, an image encryption scheme based on chaotic standard and logistic maps was proposed. Th... more Recently, an image encryption scheme based on chaotic standard and logistic maps was proposed. This paper studies the security of the scheme and shows that it can be broken with only one chosen-plaintext. Some other security defects of the scheme are also reported.
Recently, an image encryption scheme based on a compound chaotic sequence was proposed. In this p... more Recently, an image encryption scheme based on a compound chaotic sequence was proposed. In this paper, the security of the scheme is studied and the following problems are found: (1) a differential chosen-plaintext attack can break the scheme with only three chosen plain-images; (2) there is a number of weak keys and some equivalent keys for encryption; (3) the scheme is not sensitive to the changes of plain-images; and (4) the compound chaotic sequence does not work as a good random number resource.
This paper studies the security of a recently-proposed MPEG-video encryption scheme based on secr... more This paper studies the security of a recently-proposed MPEG-video encryption scheme based on secret Huffman tables. Our cryptanalysis shows that: 1) the key space of the encryption scheme is not sufficiently large against divide-and-conquer (DAC) attack and known-plaintext attack; 2) it is possible to decrypt a cipher-video with a partially-known key, thus dramatically reducing the complexity of the DAC brute-force attack in some cases; 3) its security against the chosen-plaintext attack is very weak. Some experimental results are included to support the cryptanalytic results with a brief discuss on how to improve this MPEG-video encryption scheme.
At ISCAS'2005, Yen et al. presented a new chaos-based cryptosystem for multimedia transmission na... more At ISCAS'2005, Yen et al. presented a new chaos-based cryptosystem for multimedia transmission named "Multimedia Cryptography System" (MCS). No cryptanalytic results have been reported so far. This paper presents a differential attack to break MCS, which requires only seven chosen plaintexts. The complexity of the attack is O(N), where $N$ is the size of plaintext. Experimental results are also given to show the real performance of the proposed attack.
Chaotic systems have been broadly exploited through the last two decades to build encryption meth... more Chaotic systems have been broadly exploited through the last two decades to build encryption methods. Recently, two new image encryption schemes have been pro- posed, where the encryption process involves a permutation operation and an XOR- like transformation of the shuffled pixels, which are controlled by three chaotic sys- tems. This paper discusses some defects of the schemes and how
This letter discusses some key issues and problems about multimedia encryption, leading to a call... more This letter discusses some key issues and problems about multimedia encryption, leading to a call for research in an interesting new direction of encryption-friendly multimedia coding and communications.
This paper studies the security of a secure communication scheme based on two discrete-time inter... more This paper studies the security of a secure communication scheme based on two discrete-time intermittently-chaotic systems synchronized via a common random driving signal. Some security defects of the secure communication scheme are revealed: 1) the key space can be remarkably reduced; 2) the decryption is insensitive to the mismatch of the secret key; 3) the key-generation process used in this secure communication scheme is insecure against known/chosen-plaintext attacks. The first two defects mean that the secure communication scheme is not secure enough against brute-force attacks, and the third means that an attacker can easily break the cryptosystem by approximately estimating the secret key once he has a chance to access a fragment of the generated keystream. A direct result of the cryptanalysis given in this paper is the unsuitability of intermittent chaos in the design of secure chaotic cryptosystems.
In recent years, chaotic attractors have been extensively used in the design of secure communicat... more In recent years, chaotic attractors have been extensively used in the design of secure communication systems. One of the preferred ways of transmitting the information signal is binary chaotic modulation, in which a binary message modulates a parameter of the chaotic generator. This paper presents a method of attack based on estimating the short-time period of the ciphertext generated from the modulated chaotic attractor. By calculating and then filtering the short-time period of the transmitted signal it is possible to obtain the binary information signal with great accuracy without any knowledge of the parameters of the underlying chaotic system. This method is successfully applied to various secure communication systems proposed in the literature based on different chaotic attractors.
In 1998, M. S. Baptista proposed a chaotic cryptosystem, which has attracted much attention from ... more In 1998, M. S. Baptista proposed a chaotic cryptosystem, which has attracted much attention from the chaotic cryptography community: some of its modifications and also attacks have been reported in recent years. In [Phys. Lett. A 307 , we suggested a method to enhance the security of Baptista-type cryptosystem, which can successfully resist all proposed attacks. However, the enhanced Baptista-type cryptosystem has a nontrivial defect, which produces errors in the decrypted data with a generally small but nonzero probability, and the consequent error propagation exists. In this Letter, we analyze this defect and discuss how to rectify it. In addition, we point out some newly-found problems existing in all Baptista-type cryptosystems and consequently propose corresponding countermeasures.
This paper studies so-called "null polynomials modulo m", i.e., polynomials with integer coeffici... more This paper studies so-called "null polynomials modulo m", i.e., polynomials with integer coefficients 1 that satisfy f (x) ≡ 0 (mod m) for any integer x. The study on null polynomials is helpful to reduce congruences of higher degrees modulo m and to enumerate equivalent polynomial functions modulo m, i.e., functions over Zm = {0, · · · , m − 1} generated by integer polynomials. The most well-known null polynomial is f (x) = x p − x modulo a prime p.
First International Conference on Security and Privacy for Emerging Areas in Communications Networks (SECURECOMM'05), 2005
In the past few years, a number of image encryption algorithms based on chaotic maps have been pr... more In the past few years, a number of image encryption algorithms based on chaotic maps have been proposed. A recently proposed Chaotic-Key Based Algorithm (CKBA) is based on a one-dimensional Logistic map. However, it has been shown that the current CKBA model is unavoidably susceptible to chosen/known-plaintext attacks, and that the high security claims against ciphertext-only attack were overestimated by the authors. In addition, the chaotic Logistic map yields unbalanced output. In this paper we enhance the CKBA algorithm three-fold: (1)we change the 1-D chaotic Logistic map to a piecewise linear chaotic map (PWLCM) to improve the balance property, (2)we increase the key size to 128 bits, and (3)-we add two more cryptographic primitives and extend the scheme to operate on multiple rounds so that the chosen/known-plaintext attacks are no longer possible. The new cipher has much stronger security and its performance characteristics remain very good. A security analysis for the proposed system is performed and presented.
Circuits Systems and Signal Processing, Jan 9, 2005
We have proposed a chaotic cryptographic scheme based on iterating the logistic map and updating ... more We have proposed a chaotic cryptographic scheme based on iterating the logistic map and updating the look-up table dynamically. However, it has been broken recently. In this paper, the weaknesses of the original dynamic look-up table scheme are analyzed and a more secure chaotic encryption scheme based on this dynamic look-up table concept is proposed. Theoretical analysis indicates that the modified scheme can resist the reported attacks. Moreover, simulation results show that this encryption scheme leads to a flat ciphertext distribution.
Proceedings Icip International Conference on Image Processing, Feb 8, 2010
Motivated by the work of Uehara et al. [1], an improved method to recover DC coefficients from AC... more Motivated by the work of Uehara et al. [1], an improved method to recover DC coefficients from AC coefficients of DCT-transformed images is investigated in this work, which finds applications in cryptanalysis of selective multimedia encryption. The proposed under/over-flow rate minimization (FRM) method employs an optimization process to get a statistically more accurate estimation of unknown DC coefficients, thus achieving a better recovery performance. It was shown by experimental results based on 200 test images that the proposed DC recovery method significantly improves the quality of most recovered images in terms of the PSNR values and several state-of-the-art objective image quality assessment (IQA) metrics such as SSIM and MS-SSIM.
School of Electrical Engineering Computer Science Science Engineering Faculty, Dec 7, 2009
Recently a new human authentication scheme called PAS (predicate-based authentication service) wa... more Recently a new human authentication scheme called PAS (predicate-based authentication service) was proposed, which does not require the assistance of any supplementary device. The main security claim of PAS is to resist passive adversaries who can observe the whole authentication session between the human user and the remote server.
Unimodal maps have been broadly used as a base of new encryption strategies. Recently, a stream c... more Unimodal maps have been broadly used as a base of new encryption strategies. Recently, a stream cipher has been proposed in the literature, whose keystream is basically a symbolic sequence of the (one-parameter) logistic map or of the tent map. In the present work a thorough analysis of the keystream is made which reveals the existence of some serious security problems.
Iee Proceedings Vision Image and Signal Processing, Mar 9, 2006
Recently, a VoIP (voice over Internet protocol) technique with a new hierarchical data security p... more Recently, a VoIP (voice over Internet protocol) technique with a new hierarchical data security protection (HDSP) scheme was proposed by using a secret chaotic bit sequence. This paper points out some insecure properties of the HDSP scheme, and then uses them to develop known/chosen-plaintext attacks. The following main findings are: 1) given n known plaintexts, about (100 − 50 2 n ) percent of secret chaotic bits can be uniquely determined; 2) given only one specially-chosen plaintext, all secret chaotic bits can be uniquely derived; 3) the secret key can be derived with practically small computational complexity when only one plaintext is known (or chosen). These facts reveal that HDSP is very weak against known/chosen-plaintext attacks. Experiments are given to show the feasibility of the proposed attacks. Furthermore, it is also found that the security of HDSP against the brute-force attack is not practically strong. Finally, some countermeasures are discussed for enhancing the security of HDSP, and several basic principles are suggested for the design of a secure encryption scheme.
In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped ne... more In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped neural network (CNN) for encryption. The present paper analyzes the security of this chaotic cipher against chosen-plaintext attacks, and points out that this cipher can be broken by a chosen-plaintext attack. Experimental analyses are given to support the feasibility of the proposed attack.
In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped ne... more In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped neural network (CNN) for encryption. The present paper analyzes the security of this chaotic cipher against chosen-plaintext attacks, and points out that this cipher can be broken by a chosen-plaintext attack. Experimental analyses are given to support the feasibility of the proposed attack.
Recently, an image encryption scheme based on chaotic standard and logistic maps was proposed. Th... more Recently, an image encryption scheme based on chaotic standard and logistic maps was proposed. This paper studies the security of the scheme and shows that it can be broken with only one chosen-plaintext. Some other security defects of the scheme are also reported.
Recently, an image encryption scheme based on a compound chaotic sequence was proposed. In this p... more Recently, an image encryption scheme based on a compound chaotic sequence was proposed. In this paper, the security of the scheme is studied and the following problems are found: (1) a differential chosen-plaintext attack can break the scheme with only three chosen plain-images; (2) there is a number of weak keys and some equivalent keys for encryption; (3) the scheme is not sensitive to the changes of plain-images; and (4) the compound chaotic sequence does not work as a good random number resource.
This paper studies the security of a recently-proposed MPEG-video encryption scheme based on secr... more This paper studies the security of a recently-proposed MPEG-video encryption scheme based on secret Huffman tables. Our cryptanalysis shows that: 1) the key space of the encryption scheme is not sufficiently large against divide-and-conquer (DAC) attack and known-plaintext attack; 2) it is possible to decrypt a cipher-video with a partially-known key, thus dramatically reducing the complexity of the DAC brute-force attack in some cases; 3) its security against the chosen-plaintext attack is very weak. Some experimental results are included to support the cryptanalytic results with a brief discuss on how to improve this MPEG-video encryption scheme.
At ISCAS'2005, Yen et al. presented a new chaos-based cryptosystem for multimedia transmission na... more At ISCAS'2005, Yen et al. presented a new chaos-based cryptosystem for multimedia transmission named "Multimedia Cryptography System" (MCS). No cryptanalytic results have been reported so far. This paper presents a differential attack to break MCS, which requires only seven chosen plaintexts. The complexity of the attack is O(N), where $N$ is the size of plaintext. Experimental results are also given to show the real performance of the proposed attack.
Chaotic systems have been broadly exploited through the last two decades to build encryption meth... more Chaotic systems have been broadly exploited through the last two decades to build encryption methods. Recently, two new image encryption schemes have been pro- posed, where the encryption process involves a permutation operation and an XOR- like transformation of the shuffled pixels, which are controlled by three chaotic sys- tems. This paper discusses some defects of the schemes and how
This letter discusses some key issues and problems about multimedia encryption, leading to a call... more This letter discusses some key issues and problems about multimedia encryption, leading to a call for research in an interesting new direction of encryption-friendly multimedia coding and communications.
This paper studies the security of a secure communication scheme based on two discrete-time inter... more This paper studies the security of a secure communication scheme based on two discrete-time intermittently-chaotic systems synchronized via a common random driving signal. Some security defects of the secure communication scheme are revealed: 1) the key space can be remarkably reduced; 2) the decryption is insensitive to the mismatch of the secret key; 3) the key-generation process used in this secure communication scheme is insecure against known/chosen-plaintext attacks. The first two defects mean that the secure communication scheme is not secure enough against brute-force attacks, and the third means that an attacker can easily break the cryptosystem by approximately estimating the secret key once he has a chance to access a fragment of the generated keystream. A direct result of the cryptanalysis given in this paper is the unsuitability of intermittent chaos in the design of secure chaotic cryptosystems.
In recent years, chaotic attractors have been extensively used in the design of secure communicat... more In recent years, chaotic attractors have been extensively used in the design of secure communication systems. One of the preferred ways of transmitting the information signal is binary chaotic modulation, in which a binary message modulates a parameter of the chaotic generator. This paper presents a method of attack based on estimating the short-time period of the ciphertext generated from the modulated chaotic attractor. By calculating and then filtering the short-time period of the transmitted signal it is possible to obtain the binary information signal with great accuracy without any knowledge of the parameters of the underlying chaotic system. This method is successfully applied to various secure communication systems proposed in the literature based on different chaotic attractors.
In 1998, M. S. Baptista proposed a chaotic cryptosystem, which has attracted much attention from ... more In 1998, M. S. Baptista proposed a chaotic cryptosystem, which has attracted much attention from the chaotic cryptography community: some of its modifications and also attacks have been reported in recent years. In [Phys. Lett. A 307 , we suggested a method to enhance the security of Baptista-type cryptosystem, which can successfully resist all proposed attacks. However, the enhanced Baptista-type cryptosystem has a nontrivial defect, which produces errors in the decrypted data with a generally small but nonzero probability, and the consequent error propagation exists. In this Letter, we analyze this defect and discuss how to rectify it. In addition, we point out some newly-found problems existing in all Baptista-type cryptosystems and consequently propose corresponding countermeasures.
This paper studies so-called "null polynomials modulo m", i.e., polynomials with integer coeffici... more This paper studies so-called "null polynomials modulo m", i.e., polynomials with integer coefficients 1 that satisfy f (x) ≡ 0 (mod m) for any integer x. The study on null polynomials is helpful to reduce congruences of higher degrees modulo m and to enumerate equivalent polynomial functions modulo m, i.e., functions over Zm = {0, · · · , m − 1} generated by integer polynomials. The most well-known null polynomial is f (x) = x p − x modulo a prime p.
First International Conference on Security and Privacy for Emerging Areas in Communications Networks (SECURECOMM'05), 2005
In the past few years, a number of image encryption algorithms based on chaotic maps have been pr... more In the past few years, a number of image encryption algorithms based on chaotic maps have been proposed. A recently proposed Chaotic-Key Based Algorithm (CKBA) is based on a one-dimensional Logistic map. However, it has been shown that the current CKBA model is unavoidably susceptible to chosen/known-plaintext attacks, and that the high security claims against ciphertext-only attack were overestimated by the authors. In addition, the chaotic Logistic map yields unbalanced output. In this paper we enhance the CKBA algorithm three-fold: (1)we change the 1-D chaotic Logistic map to a piecewise linear chaotic map (PWLCM) to improve the balance property, (2)we increase the key size to 128 bits, and (3)-we add two more cryptographic primitives and extend the scheme to operate on multiple rounds so that the chosen/known-plaintext attacks are no longer possible. The new cipher has much stronger security and its performance characteristics remain very good. A security analysis for the proposed system is performed and presented.
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