Active learning plays an important role for boosting interactive image retrieval.Among various methods,support vector machine(SVM) based active learning approaches have been drawn substantial attention.However,most SVM-based active learning methods are challenged by small example problem,asymmetric distribution problem,and redundancy among examples.This paper proposed two mechanisms to tackle above problems:(1) designing an asymmetric semi-supervised learning(ASL) framework that exploits unlabeled data for semantic relevant and irrelevant classes in different ways.Under the influence of ASL,the efficiency of SVM is significantly improved;and(2) developing a representative measure based active selection criterion to identify the most informative images from unlabeled data while the diversity among them is augmented.Experimental results validate the superiority of our scheme over several existing methods.

Block ciphers based on key-dependent cipher structures have been investigated for years,however,their overall performance in terms of security and speed has not been sufficiently addressed.We proposed a 128-bit Feistel block cipher,which engages both dynamic S-box and dynamic P-boxes that are all key-depen-dent.With these two key-dependent transformations,the internal structure of this cipher algorithm was secured,so as to resist the linear and differential cryptanalysis in a few round encryptions.Hence,the encryption and decryption functions are very efficient.We named this key-dependent structure the DSP structure,and the cipher DSP.A fast permutation algorithm was used to generate both the dynamic S-box and dynamic P-boxes.This greatly compensates the performance penalty of complex key schedule.The basic operations selected in DSP are all efficient bytewise operations,so the algorithm will have a reasonable fast speed on recent processors,16-bit processors and smart cards as well as 8-bit processors.We implemented the algorithm with C and Java on two different PCs with Pentium processors,and estimated the optimized assembly performance.The experimental results and the estimation show that DSP has a very fast encryption/decryption speed and a reasonable fast key scheduling implementation.

In this paper, a novel semi-fragile watermarking scheme for image authentication is proposed. The watermark is extracted from the feature of the original image by adaptive gradient partitioning. Then the watermark is inserted back into the image by modulating the wavelet coefficients. In order to increase the robustness and invisibility of the watermarking scheme, the quantization step is calculated in accordance with the local image feature. The integrity authentication and tamper detection are implemented by comparing the newly extracted image feature and the extracted watermark. From the experimental result we see that if there is no change in the watermarked image, the watermark will be correctly extracted, thus will pass the authentication. But malicious changes of the image will breach the watermark and fail the authentication. This scheme is tolerant of regular manipulations, such as JPEG2000 compression. By using a watermark denoising method, our scheme can detect the exact locations, which are illegally modified. In addition, it can also detect some special attacks (such as alternation of the intensity of flat image area and completely eliminate an object), which can not be detected by most existing semi-fragile watermark schemes.

Block ciphers based on key-dependent cipher structures have been investigated for years, however, their overall performance in terms of security and speed has not been sufficiently addressed. In this paper, we propose a 128-bit Feistel block cipher, which simultaneously engages key-dependent S-box and key-dependent P-box. With these two key-dependent transformations, the internal structure of this cipher algorithm is secured, so as to resist the linear and differential cryptanalysis in a few round encryptions. Hence, the encryption and decryption functions are quite efficiency. We named this key-dependent structure the DSDP structure, and the cipher DSDP. A fast permutation algorithm is used to generate both the key-dependent S-box and key-dependent P-boxes. This greatly compensates the performance penalty of complex key schedule. The basic operations used in DSDP are all efficient bytewise operations, so the algorithm will have a reasonable fast speed on recent processors, 16-bit processors and smart cards as well as 8-bit processors. We implement the algorithm with C and Java respectively on several PCs with different processors, and estimate the optimized assembly performance on Pentium. The experimental results and the estimation show that DSDP has a very fast encryption/decryption speed and a reasonable fast key scheduling implementation.

Most important things of secure communications are integrity and confidentiality. However, seldom cipher mode could achieve these two goals simultaneously. So, in this paper, a novel cipher mode is proposed to solve this scheme. The newly proposed mode is based on a previous work PCBC, which has the vulnerability that it permits the modification of swapping two ciphertext, which could pass the integrity authentication. In our algorithm, by adding another XOR operation with a counter to the mode, we successfully solve the vulnerability of PCBC, so we named it C-PCBC. In addition, our algorithm could be more efficient than another modification M-PCBC, thus it will be very useful in the case where confidentiality and integrity are both needed.

Block ciphers based on key-dependent cipher structures have been investigated for years, however, their overall performance in terms of security and key-setup speed has not been sufficiently addressed. In this paper, we propose a 128-bit block cipher based on a novel SPN structure, which uses both S-box and P-boxes that are all key-dependent. With these two key-dependent transformations, the internal structure of this cipher algorithm is hided from the cryptanalyst, so as to resist the linear and differential cryptanalysis in a few round encryptions. We named this key-dependent structure the DSDP structure, and the cipher DSDP. A fast permutation algorithm is used to generate both the key-dependent S-box and key-dependent P-boxes. This greatly compensates the performance penalty of complex key schedule. The experimental results show that our algorithm has a very fast encryption/decryption speed and a reasonable fast key scheduling implementation.