In this research, we have tried to first focus on the previous work and after getting familiar with the base papers, focus on the main paper. In this paper, we try to determine the security problems in the proposed protocols and present appropriate solutions for them. One of the subjects studied by security and encryption researchers is the matter of authentication and key agreement in SIP. Recently, an authentication and key agreement protocol in SIP has been presented in a scheme. In this paper, it was proven that their presented protocol is vulnerable to the replay attack. Such that if an attacker resends the messages sent on the public channel back to the server, the server does not notice the duplicate messages and proceeds with the session process. Also, their protocol is not resistant to the temporary parameter disclosure attack and it is possible for the attacker to discover the session key in case the temporary parameters are disclosed. Furthermore, user anonymity does neither provide re-registration prevention with the real user ID nor early detection. In this paper, we have tried to present a protocol which prevents replay and parameter disclosure attacks.
The purpose of the present study was to examine the effects of easy goals versus difficult goals on acquisition and retention of basketball free throws in children with intellectual disability. Twenty-one children with intellectual disability were randomly assigned to an easy goals or difficult goals group. The participants were required to improve their basketball free throws according to their own scores in the previous exercise session. More difficult goals were set for the difficult goals group than for the easy goals group. The groups exercised the task for nine sessions. Both groups performed pretest, acquisition, and retention tests. Results showed that participants with easy goals improved their performance while the participants with difficult goals failed to improve their performance. These findings indicate that providing children with intellectual disability with easy goals facilitates the process of sport skill learning.
A series of novel (E)-5,5-dimethyl-3-styrylcyclohex-2-en-1-ol dienes were synthesized by reduction of the respective ketones and their Diels-Alder reactivity explored with Nphenylmaleimide and methyl acrylate. Consequently, two groups of novel products were synthesized in high yields. In reactions with N-phenylmaleimide, the initially formed cycloadducts undergo an additional in situ lactonization to give tricyclic lactone systems, due to spontaneous attack of the allylic hydroxyl on the neighboring carbonyl group of the dienophile residue. All reactions proceeded stereoselectively to give solely the endo products.
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