ABSTRACT A physical unclonable function is a one-way function with a mapping determined by uncontrolled, but static, variations of a physical object. A PUF can be used for storage-less cryptographic key generation and authentication. The challenges of engineering a PUF is to make it stable, unique, unclonable, unpredictable and one-way. This poster describes several recent results in this project, including a microprocessor-based PUF, a method to analyze aging effects in PUFs, and a public database to store PUF data for evaluation.