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.
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.
26132055
Car Plate Localization Using Pulse Coupled Neural Network in Complicated Environment
Car plate recognition is an important problem in many traffic related applications. In this paper, we focus on car plate localization-the first step of car plate recognition. We propose a hybrid method based on Pulse Coupled Neural Network (PCNN) and wavelet analysis. First of all, we use PCNN to enhance the image. Then, regions of interest (ROIs) will be get through wavelet analysis. After that, PCNN enhancement is applied again in ROIs, followed by a training and classification process for final labelling ROIs as car plate regions or not. Experiment results show that the precision can get 96%, which is higher than other localization methods on the same image database.
45286898
TMAC: Taint-Based Memory Protection via Access Control
Memory corruption attacks account for most parts of malicious attacks toward software security. Recently dynamic taint analysis is proposed and is gaining momentum. This proposed technique attempts to defeat attacks by checking the taintedness and integrity of pointers when accessing memory since vulnerabilities are always motivated by tainting pointers. Unfortunately, there exists some class of attacks without tainting pointers, such as array bounds violation attacks using pointers. In this paper, we propose a novel approach to defeat this kind of undetected attacks using taint-based tracking analysis. Our notion is based on the memory access control, that is, first, we will check the taintedness of the pointers when accessing memory like existing taint-based approaches, second, we will check whether or not the memory area is in the legitimate range of a pointer used to access this memory. Our implementation dose not need source code and is based on Valgrind, hence works on commodity software. To demonstrate our idea, we performed a preliminary empirical experiments, the results are quite promising: TMAC can effectively detect a wide range of attacks, and the average runtime overhead is close to Memcheck, a widely memory error detector.
46712099
Side Information Inserted Pilot Tone Transmission for PAPR Reduction in OFDM
In order to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals over fading channels, the selected mapping (SLM) scheme and channel estimation technique can be used. Because of the side information of SLM, however, the data rate decreases in the conventional transmission method. In this letter, to overcome this impairment, we propose a technique which transmits side information by using pilot tones. Numerical analysis and computer simulations show that this method can maintain the PAPR reduction ability of SLM while improving error performance.
28547446
Low-Complex Equalization for Single Carrier Systems Employing Cyclic Prefix over Time-Variant Channels
A simplified equalization method based on the band structure of the frequency domain channel matrix is proposed for the single carrier systems employing cyclic prefix (SC-CP) over time-varying wireless channels. Using both theoretical analysis and computer simulation, it is shown that the complexity of this method is proportional to the number of symbols in one SC-CP block and is less than that of traditional block equalization methods. We also show that they have similar performance.
15237813
Research on an Immune Mechanism Based Intelligent Spam Filter
With regard to the problem that the traditional antispam filter is usually incapable of recognizing unknown and mutational characters, a novel anti-spam filter based on immune mechanisms is proposed which employs multiple principles and mechanisms of the artificial immune system, such as the self tolerance, immune recognition, immune learning and immune memory. Through combining the idea of intelligent decision support system with the extension of classical rough set theory, a novel algorithm is provided for finding minimal attributes extraction and updating the attributes base. Simulation shows that this technique is able to reduce and improve the availability of the normal anti-spam systems.