This thesis is a collection of three different research contributions targeted towards providing faster message authentication for long messages which have been recently accepted or submitted for publication. The first research work explores properties of Multiple Input Shift Register (MISR) as a universal hash function. We implemented a fixed length message authentication code (MAC) based on MISR in software. Signing or verification time of new MAC is two order less compared to existing MAC. The second contribution is a variable length MAC based on MISR for use in smart grid networks. We prove security of the MAC scheme and analyze its performance pertaining to smart grid application.The third contribution suggests use of one-time signatures (OTS) from sigma protocols for multicast authentication in smart grid. The proposed scheme yields three order improvements in time performance at a very modest increase in signature size compared to currently best known OTS scheme.