In recent years, IP protection of FPGA hardware designs has become a requirement for many IP vendors. To this end solutions have been proposed based on the idea of bitstream encryption, symmetric-key primitives, and the use of Physical Unclonable Functions (PUFs). In this paper, we propose new protocols for the IP protection problem on FPGAs based on public-key (PK) cryptography, analyze the advantages and costs of such an approach, and describe a PUF intrinsic to current FPGAs based on SRAM properties. We observe that a major advantage in using PK-based protocols is that it allows for an implementation in which the private key stored in the FPGA never has to leave the device, thus increasing security. Finally, notice that this comes at the cost of additional hardware resources but not at significant performance degradation.