In this work, we look into several aspects of hardware security. The major part of this thesis is dedicated to true random number generators (TRNGs). Our contributions to this field include designing a novel all-digital entropy source and developing a methodology for efficient online testing. Part of the work was dedicated to experimental evaluation of physically unclonable functions (PUFs) cryptographic primitives used for device authentication and countermeasures against device counterfeiting. Side channel attacks such as power-analysis are another significant threat to embedded security. Circuit-level countermeasures against the power analysis were applied in designing an embedded processor for elliptic curve cryptography (ECC) and in designing a side-channel secure SRAM-cell.