We present a lightweight pseudorandom number generator (PRNG) design for EPC Gen2 RFID tags. It is based on a linear feedback shift register (LFSR) configured with multiple feedback polynomials that are selected by a physical source of randomness. The proposal successfully handles the inherent linearity of LFSR based PRNGs and satisfies the statistical requirements imposed by the EPC Gen2 standard. Statistical analysis of the sequences generated by our generator confirms the validity of the proposed technique.We show that our proposal has, moreover, a simpler hardware implementation and energy consumption than previous designs reported in the literature.