RFID (Radio Frequency Identification) is one of the most growing technologies among the pervasive systems. Non line of sight capability makes RFID systems much faster than its other contending systems such as barcodes and magnetic taps etc. But there are some allied security apprehensions with RFID systems. RFID security has been acquired a lot of attention in last few years as evinced by the large number of publications (over 3000). In this paper, a brief survey of eminent ultralightweight authentication protocols has been presented & then a four-layer security model, which comprises of various passive and active attacks, has been proposed. Finally, Cryptanalysis of these protocols has also been performed under the implications of the proposed security model
