Virtually all applications which provide or require a security service need a secret key. In an ambient world, where (potentially) sensitive information is continually being gathered about us, it is critical that those keys be both securely deployed and safeguarded from compromise. In this paper, we provide solutions for secure key deployment and storage of keys in sensor networks and radio frequency identification systems based on the use of Physical Unclonable Functions (PUFs). In addition, to providing an overview of different existing PUF realizations, we introduce a PUF realization aimed at ultra-low cost applications. We then show how the properties of Fuzzy Extractors or Helper Data algorithms can be used to securely deploy secret keys to a low cost wireless node. Our protocols are more efficient (round complexity) and allow for lower costs compared to previously proposed ones. We also provide an overview of PUF applications aimed at solving the counterfeiting of goods and devices.