Low cost devices such as RFIDs, sensor network nodes, and smartcards are crucial for building the next generation pervasive and ubiquitous networks. The inherent power and footprint limitations of such networks, prevent us from employing standard cryptographic techniques for authentication which were originally designed to secure high end systems with abundant power. Furthermore, the sharp increase in the number, diversity and strength of physical attacks which directly target the implementation may have devastating consequences in a network setting creating a single point of failure. A compromised node may leak a master key, or may give the attacker an opportunity for injecting faulty messages. In this paper we present a lightweight challenge response authentication scheme based on noisy physical unclonable functions (PUF) that allows for extremely efficient implementations. Furthermore, the inherent properties of PUFs provide cryptographically strong tamper resilience. In a network setting this means that a tampered device will no longer authenticate and in a sense will be isolated from the network.