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.
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.
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.
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.
8484163
Near-Collision Attacks on MD4: Applied to MD4-Based Protocols
The most widely used hash functions from MD4 family have been broken, which lead to a public competition on designing new hash functions held by NIST. This paper focuses on one concept called near-collision resistance: computationally difficult to find a pair of messages with hash values differing in only few bits, which new hash functions should satisfy. In this paper, we will give a model of near-collisions on MD4, and apply it to attack protocols including HMAC/NMAC-MD4 and MD4(Password||Challenge). Our new outer-key recovery attacks on HMAC/NMAC-MD4 has a complexity of 272 online queries and 277 MD4 computations, while previous result was 288 online queries and 295 MD4 computations. Our attack on MD4(Password||Challenge) can recover 16 password characters with a complexity of 237 online queries and 221 MD4 computations, which is the first approach to attack such protocols.
35028524
SmartOSEK: A Real-Time Operating System for Automotive Electronics
This paper puts forward SmartOSEK, a dependable platform for automobile electronics, which consists of an operating system compliant with OSEK/VDX specifications and an integrated development environment (IDE) that consists of many convenient tools, such as visual designer, system generator, time analyst, scheduling analyst, and running tracer. In the operating system, SmartOSEK OS and SmartOSEK COM are presented. In the IDE, we apply the graphic design, automatic code generation and time analysis to help developers devote their mind to the modeling of the applications. A design example of automated transmission system based on SmartOSEK platform is given, and good results are achieved.
17672081
A Sub-Vector Weighting Scheme for Image Retrieval with Relevance Feedback
In image retrieval with relevance feedback, feature components are weighted to reflect the high-level concepts, and a user's subjective perception, embodied in the images labelled by the user in the feedback. However, the number of labelled images is often small and the covariance matrix needed for weighting will be singular. For this reason, the commonly used methods discard the mutual correlation among the feature components completely and use a diagonal covariance matrix. In this paper, a sub-vector weighting scheme is proposed. This scheme partitions a multi-dimensional visual feature vector into multiple low-dimensional sub-vectors. The singularity of the covariance matrix for each sub-vector can be avoided due to the lower dimensionality of the sub-vectors. Thus, the mutual correlation in each sub-vector can be retained for weighting and an optimally weighted similarity metric can be applied on each sub-vector. The similarity scores obtained from different sub-vectors are combined, as the final scor...
14161644
A Fast Algorithm for Creating a Compact and Discriminative Visual Codebook
In patch-based object recognition, using a compact visual codebook can boost computational efficiency and reduce memory cost. Nevertheless, compared with a large-sized codebook, it also risks the loss of discriminative power. Moreover, creating a compact visual codebook can be very time-consuming, especially when the number of initial visual words is large. In this paper, to minimize its loss of discriminative power, we propose an approach to build a compact visual codebook by maxi- mally preserving the separability of the object classes. Furthermore, a fast algorithm is designed to accomplish this task effortlessly, which can hierarchically merge 10,000 visual words down to 2 in ninety seconds. Experimental study shows that the compact visual codebook created in this way can achieve excellent classification performance even after a considerable reduction in size.
46259333
PN-based Security Design for Data Storage
For improving the security and privacy of data storage, a novel model based on code division multiple access, called PNCD-DS, is proposed for dealing with the problem of resources sharing in a storage area network (SAN). This technology differs from existing such as spac e or time division multiple access, it has some essential features for ensuring the security and privacy of user's information and/or data. Through decreasing the information intensity by multi times during user's data storage and then recovering it normal when scan, the method makes the interference from other users or damages to the data weaken enormously. Therefore, damage to some extent in some local area of SAN will not destroy the integrity of saved data. On the other hand, because a SAN here can be regarded exclusive for each user with its own special code, the data management could be simplified. Due to coded when data storage and/or backup and decoded when scan, the probability of user's data leakage is also very low even if the disk is physical ly handed by some other users. Key Words Security, confidentiality, database, storage area network, PN sequence
15434765
A Dynamic Sub-vector Weighting Scheme for Image Retrieval with Relevance Feedback
In image retrieval with relevance feedback, feature components obtained from low-level descriptors are often weighted to reflect the high-level concepts and a user’s subjective perception embodied in the images labelled by the user in the feedback. However, the number of the labelled images is often small and an optimal weighting cannot be achieved in practice because of the singularity of the covariance matrix needed for weighting. To solve this problem, a dynamic sub-vector weighting scheme is proposed in this paper. In this scheme, a multi-dimensional feature vector is partitioned into multiple sub-vectors whose dimensions are dynamically adjusted to match the small number of available labelled images. Because of the lower dimensionality of the sub-vectors, the optimal weighting can be performed based on these sub-vectors, respectively. The multiple similarity scores obtained from sub-vector comparisons are then combined, as the final score, to rank the database images and determine the retrieval result. Experimental results demonstrated better performance of the proposed weighting scheme than some existing weighting schemes.