32346693
New Message Difference for MD4
This paper proposes several approaches to improve the collision attack on MD4 proposed byWang et al. First, we propose a new local collision that is the best for the MD4 collision attack. Selection of a good message difference is the most important step in achieving effective collision attacks. This is the first paper to introduce an improvement to the message difference approach of Wang et al., where we propose a new local collision. Second, we propose a new algorithm for constructing differential paths. While similar algorithms have been proposed, they do not support the new local collision technique. Finally, we complete a collision attack, and show that the complexity is smaller than the previous best work.
31093950
Extended Password Recovery Attacks against APOP, SIP, and Digest Authentication
In this paper, we propose password recovery attacks against challenge-response authentication protocols. Our attacks use a message difference for a MD5 collision attack proposed in IEICE 2008. First, we show how to efficiently find a message pair that collides with the above message difference. Second, we show that a password used in authenticated post office protocol (APOP) can be recovered practically. We also show that the password recovery attack can be applied to a session initiation protocol (SIP) and digest authentication. Our attack can recover up to the first 31 password characters in a short time and up to the first 60 characters faster than the naive search method. We have implemented our attack and confirmed that 31 characters can be successfully recovered.
10157835
New Message Differences for Collision Attacks on MD4 and MD5
In 2005, collision resistance of several hash functions was broken by Wang et al. The strategy of determining message differences is the most important part of collision attacks against hash functions. So far, many researchers have tried to analyze Wang et al.'s method and proposed improved collision attacks. Although several researches proposed improved attacks, all improved results so far were based on the same message differences proposed by Wang et al. In this paper, we propose new message differences for collision attacks on MD4 and MD5. Our message differences of MD4 can generate a collision with complexity of less than two MD4 computations, which is faster than the original Wang et al.'s attack, and moreover, than the all previous attacks. This is the first result that improves the complexity of collision attack by using different message differences from Wang et al.'s. Regarding MD5, so far, no other message difference from Wang et al.'s is known. Therefore, study for constructing method of other message differences on MD5 should be interesting. Our message differences of MD5 generates a collision with complexity of 242 MD5 computations, which is slower than the latest best attack. However, since our attack needs only 1 bit difference, it has some advantages in terms of message freedom of collision messages.
14024123
Visual Secret Sharing Schemes for Multiple Secret Images Allowing the Rotation of Shares
In this paper, a method is proposed to construct a visual secret sharing (VSS) scheme for multiple secret images in which each share can be rotated with 180 degrees in decryption. The proposed VSS scheme can encrypt more number of secret images compared with the normal VSS schemes. Furthermore, the proposed technique can be applied to the VSS scheme that allows to turn over some shares in decryption. From the theoretical point of view, it is interesting to note that such VSS schemes cannot be obtained from so-called basis matrices straightforwardly.
37423199
How to Confirm Cryptosystems Security: The Original Merkle-Damgård Is Still Alive!
At Crypto 2005, Coron et al. showed that Merkle-Damgard hash function (MDHF) with a fixed input length random oracle is not indifferentiable from a random oracle RO due to the extension attack. Namely MDHF does not behave like RO. This result implies that there exists some cryptosystem secure in the RO model but insecure under MDHF. However, this does not imply that no cryptosystem is secure under MDHF. This fact motivates us to establish a criteria methodology for confirming cryptosystems security under MDHF. 
 
In this paper, we confirm cryptosystems security by using the following approach: 1 Find a variant, $\widetilde{\mathsf{RO}}$, of RO which leaks the information needed to realize the extension attack. 
 1 Prove that MDHF is indifferentiable from $\widetilde{\mathsf{RO}}$. 
 1 Prove cryptosystems security in the $\widetilde{\mathsf{RO}}$ model. 
 From the indifferentiability framework, a cryptosystem secure in the $\widetilde{\mathsf{RO}}$ model is also secure under MDHF. Thus we concentrate on finding $\widetilde{\mathsf{RO}}$, which is weaker than RO. 
 
We propose the Traceable Random Oracle (TRO) which leaks enough information to permit the extension attack. By using TRO, we can easily confirm the security of OAEP and variants of OAEP. However, there are several practical cryptosystems whose security cannot be confirmed by TRO (e.g. RSA-KEM). This is because TRO leaks information that is irrelevant to the extension attack. Therefore, we propose another $\widetilde{\mathsf{RO}}$, the Extension Attack Simulatable Random Oracle, ERO, that leaks just the information needed for the extension attack. Fortunately, ERO is necessary and sufficient to confirm the security of cryptosystems under MDHF. This means that the security of any cryptosystem under MDHF is equivalent to that under the ERO model. We prove that RSA-KEM is secure in the ERO model.
16195917
New Key-Recovery Attacks on HMAC/NMAC-MD4 and NMAC-MD5
At Crypto '07, Fouque, Leurent and Nguyen presented full key-recovery attacks on HMAC/NMAC-MD4 and NMAC-MD5, by extending the partial key-recovery attacks of Contini and Yin from Asiacrypt '06. Such attacks are based on collision attacks on the underlying hash function, and the most expensive stage is the recovery of the socalled outer key. In this paper, we show that the outer key can be recovered with near-collisions instead of collisions: near-collisions can be easier to find and can disclose more information. This improves the complexity of the FLN attack on HMAC/NMAC-MD4: the number of MAC queries decreases from 288 to 272, and the number of MD4 computations decreases from 295 to 277. We also improved the total complexity of the related-key attack on NMAC-MD5. Moreover, our attack on NMAC- MD5 can partially recover the outer key without the knowledge of the inner key, which might be of independent interest.
16013630
Runtime Performance of Parallel Array Assignment: An Empirical Study
Generating code for the array assignment statement of High Performance Fortran (HPF) in the presence of block-cyclic distributions of data arrays is considered difficult, and several algorithms have been published to solve this problem. We present a comprehensive study of the run-time performance of the code these algorithms generate. We classify these algorithms into several families, identify several issues of interest in the generated code, and present experimental performance data for the various algorithms. We demonstrate that the code generated for block-cyclic distributions runs almost as efficiently as that generated for block or cyclic distributions.
16077263
The IIR Submission to CSLP 2006 Speaker Recognition Evaluation
This paper describes the design and implementation of a practical automatic speaker recognition system for the CSLP speaker recognition evaluation (SRE). The speaker recognition system is built upon four subsystems using speaker information from acoustic spectral features. In addition to the conventional spectral features, a novel temporal discrete cosine transform (TDCT) feature is introduced in order to capture long-term speech dynamic. The speaker information is modeled using two complementary speaker modeling techniques, namely, Gaussian mixture model (GMM) and support vector machine (SVM). The resulting subsystems are then integrated at the score level through a multilayer perceptron (MLP) neural network. Evaluation results confirm that the feature selection, classifier design, and fusion strategy are successful, giving rise to an effective speaker recognition system.
16999855
A practical approach to modeling skin effect in on-chip interconnects
A compact modeling methodology for the skin effect in conductors with rectangular cross section is presented. Possible equivalent circuit topologies are reviewed, and their calibration on numerical simulation is discussed, highlighting the shortcomings of conventional calibration procedures. A new approach, based on the direct fitting of the impedance transfer function to numerical simulations, is shown to offer excellent accuracy for a wide range of cross-sectional wire aspect ratios. The new formulation also obviates the need for separating the wire internal and external inductances which is a prerequisite for all published models. Finally, a practical implementation of the model as an RL parallel network is presented.
14879086
The Algorithm of Obtaining Best Rules Based on Rough Set
With the fast development of the technology in Database and Internet, excessive information has become a problem that decision makers engage in electronic commerce have to affront. This paper firstly establishes the decision table for excessive data, then reduces knowledge of the decision table, and obtains the best rules. This can reduce the redundancy of the data, and improve the efficiency of knowledge obtaining. Because of the high time complexity and spatial complexity the general algorithm has, this paper proposed a new algorithm based on analogical matrix, and carried out the algorithm. The practice proves that the algorithm can improve the efficiency of knowledge obtaining, and the rules is tidy and best.
16763535
Handling Significant Scale Difference for Object Retrieval in a Supermarket
We propose an object retrieval application which can retrieve user specified objects from a big supermarket. Significant and unpredictable scale difference between the query and the database image is the major obstacle encountered. The widely used local invariant features show their deficiency in such an occasion. To improve the situation, we first design a new weighting scheme which can assess the repeatability of local features against scale variance. Also, another method which deals with scale difference through retrieving a query under multiple scales is also developed. Our methods have been tested on a real image database collected from a local supermarket and outperform the existing local invariant feature based image retrieval approaches. A new spatial check method is also briefly discussed.