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Abstract: In this paper, a novel geometric active contour model for color image is presented. It combines squared local contrast based alignment term about directional information of edge location as part of driving force, together with the improved geodesic active contour model containing Bays error based two-region segmentation information. And all these measures are integrated as a unified framework. Finally, an unconditionally stable and simple numerical scheme, including the narrow band and fast marching methods, is introduced for efficiently implementing this novel model. Experimental results on color image segmentation show that it can extract the contour of color images precisely and its performance is shown much better than the geodesic-aided C–V (GACV) method when directional information about edge location is supplied. [Copyright &y& Elsevier]

Abstract: Tzeng et al. proposed a new threshold multi-proxy multi-signature scheme with threshold verification. In their scheme, a subset of original signers authenticates a designated proxy group to sign on behalf of the original group. A message m has to be signed by a subset of proxy signers who can represent the proxy group. Then, the proxy signature is sent to the verifier group. A subset of verifiers in the verifier group can also represent the group to authenticate the proxy signature. Subsequently, there are two improved schemes to eliminate the security leak of Tzeng et al.’s scheme. In this paper, we have pointed out the security leakage of the three schemes and further proposed a novel threshold multi-proxy multi-signature scheme with threshold verification. [Copyright &y& Elsevier]