The perceptual image hashing is an emerging technique which can be used in image authentication and contentbased image retrieval. Recently, several image hashing schemes based on Radon transform are proposed for image authentication and retrieval. These schemes have no random information to strengthen the security with image hashing. In this paper, we propose a simple key-based secure image hashing scheme by using radon transform and 1-D Discrete Cosine Transform (DCT). Particularly, we introduce a randomization on Radon transform and make the image hash more secure and more robust. Moreover, the discriminative capability is also confirmed in our experimental results.

Abstract. In this paper we introduce the notion of certificateless proxy re-encryption and also give precise definitions for secure certificateless proxy re-encryption schemes. We present a concrete scheme based on bilinear pairing, which enjoys the advantages of certificateless public key cryptography while providing the functionalities of proxy re-encryption. Moreover, the proposed scheme is unidirectional and compatible with current certificateless encryption deployments. Finally, we show that our scheme has chosen ciphertext security in the random oracle model.

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We consider a single-server retrial queueing system where retrial time is inversely proportional to the number of customers in the system. A necessary and sufficient condition for the stability of the system is found. We obtain the Laplace transform of virtual waiting time and busy period. The transient distribution of the number of customers in the system is also obtained.

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Abstract. The confidential access to medical images becomes significant in recent years. In this paper, we propose two types of region-based selective encryption schemes to achieve secure access for medical images. The first scheme randomly flips a subset of the bits belonging to the coefficients in a Region of Interest inside of several wavelet sub-bands, which is performed in compression domain but only incurs little loss on compression efficiency. The second scheme employs AES to encrypt a certain region's data in the code-stream. The size of encrypted bit-stream is not changed and there is no compression overhead generated in the second scheme. Moreover, both of two schemes support backward compatibility so that an encryption-unaware format-compliant player can play the encrypted bit-stream directly without any crash.

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