Efficient Certificateless Signcryption in the Standard Model: Revisiting Luo and Wan’s Scheme from Wireless Personal Communications (2018)

Certificateless public key cryptography (CL-PKC) promises a practical resolution in establishing practical schemes, since it addresses two fundamental issues, namely the necessity of requiring certificate managements in traditional public key infrastructure (PKI) and the key escrow problem in identity-based (ID-based) setting concurrently. Signcryption is an important primitive that provides the goals of both encryption and signature schemes as it is more efficient than encrypting and signing messages consecutively. Since the concept of certificateless signcryption (CL-SC) scheme was put forth by Barbosa and Farshim in 2008, many schemes have been proposed where most of them are provable in the random oracle model (ROM) and only a few number of them are provable in the standard model. Very recently, Luo and Wan (Wireless Personal Communication, 2018) proposed a very efficient CL-SC scheme in the standard model. Furthermore, they claimed that their scheme is not only more efficient than the previously proposed schemes in the standard model, but also it is the only scheme which benefits from known session-specific temporary information security (KSSTIS). Therefore, this scheme would indeed be very practical. The contributions of this paper are 2-fold. First, in contrast to the claim made by Luo and Wan, we show that unfortunately Luo and Wan made a significant error in the construction of their proposed scheme. While their main intention is indeed interesting and useful, the failure of their construction has indeed left a gap in the research literature. Hence, the second contribution of this paper is to fill this gap by proposing a CL-SC scheme with KSSTIS, which is provably secure in the standard model.

DUAL BAND SECTORIAL SLOT PAC-MAN ANTENNA BY USING POLYPROPYLENE SUBSTRATE

In this paper, sectorial and circular slot Pac-man antenna for dual band frequency, 1.7 GHz for indoor wireless personal communications and 2.45 GHz Industrial science and medical (ISM) was proposed by using polypropylene (PP) flat pressed temperature con-trolled method. The method and material was chosen to reduce the overall cost and proposed new substrate with density =0.9gcm-3, dielectric constant = 2.57 and loss tangent = 0.0352.The dual band operation was distributed by sectorial slot design with, small circular slot to control and tuning the operating frequency. The back to back comparison between normal circular patch with Pac-man antenna using proposed substrate are dis-cussed and overall result distributed that there is no significant changes for gain, directivity, efficiency, vswr and physical size even though the proposed Pac-man antenna perform for dual band operation hence it is al-so improve the bandwidth of 17% compared to normal circular patch. The final Pac-man design fabricated using proposed polypropylene substrate (PP100) was then analyzed by using OTA-500 ATENLAB anechoic chamber.