Education is very important to improve the quality of life of every person. In education we are taught many things ranging from the value of life, general knowledge, morals and a variety of other sciences. In education there is the term KBM (Teaching and Learning Activities) where there are students and teachers who are connected in the delivery of knowledge or information as we know it happens in schools. But lately a virus outbreak has arisen that is troubling the world's population. Covid-19 virus or coronavirus is a disease originating from China and experts state that strong indications that the cause of SARS, this virus causes respiratory infections that spread through respiratory secretions, then the nose in the walls of the upper respiratory tract, some facts mention that this coronavirus raises many deaths. In this case, the government rules out to stop any activities and switch to stay and do activities at home. All institutions are closed as well as the world of education. So it switches to studying at home using an online system. For this reason, this study was conducted with the aim of knowing the effect of the co-19 pandemic in teaching and learning activities, especially the MI/SD level. This research was conducted at the home of each writer precisely in Bojonegoro, Lamongan, Sidoarjo and Surabaya by observing younger siblings who were still in elementary/MI school on March 17 to 18 April 2020. This study used a qualitative methodology. The data collection techniques using interviews, observation and documentation. Based on the results of the study note that social media is a science in learning activities during the co-19 pandemic, but in addition to being a bridge of knowledge, social media also has a negative influence on elementary school age children. Therefore the role of parents is very important in supervising children during the online learning process because elementary school age children/MIs are still at an unstable level and very much need guidance in carrying out online-based learning so that nothing unexpected happens.

In this paper, we propose an enhanced approach based on first-hand reputation with allows to detected misbehavior node in Manet. The network's security is an important challenge in this kind of networks. The main objective of the misbehaving nodes in AODV routing protocol deletes all data packets that received thus, don't transmit to their destination. In a reputation-based system, each node overhears the activity of its neighbors (transmit and receive) in first-hand or combined with second-hand. Our approach is composed of three-phase directly monitoring, calculating reputation value and node isolation. The reputation value is enhanced by the packet dropped due to other events such as overloading of queue and node availability. The node with a negative reputation will be isolated, and an alert packet will be distributed to neighboring nodes to inform, afterwards an improved local repair is started. The simulation results show that the proposed approach can detect and isolate a malicious node, which improves the packet delivery ratio and lowest increasing in the throughput, while reducing the success rate of the misbehaving nodes.

Providing secure communications in mobile ad hoc networks (MANET) is an important and difficult problem, due to a lack of a key management infrastructure. The authentication is an important security service in (MANETs). To provide a node authentication service we use a fully distributed certificate authorities (FDCA) based on the threshold cryptography. In this paper we propose an efficient and verifiable multi secret sharing scheme in cluster-based MANET with a low computation system. Our scheme is based on the overdetermined linear system equation in Galois fields GF(2 r). We have analyzed our scheme based on security and performance criteria, and compared with existing approaches. The efficiency of our proposed schemes was verified and evaluated by simulation. Simulation results show that this approach is scalable.