The growing connectivity offered by constrained computing devices signals a critical need for public-key cryptography in such environments. By their nature, however, public-key systems have been difficult to implement in systems with limited computational power. The NTRU public-key cryptosystem addresses this problem by offering better computational performance than previous practical systems. The efficiency of NTRU is applied to a wide variety of constrained devices in this paper, including the Palm Computing Platform, Advanced RISC Machines ARM7TDMI, the Research in Motion pager, and finally, the Xilinx Virtex 1000 family of FPGAs. On each of these platforms, NTRU offers exceptional performance, enabling a new range of applications to make use of the power of public-key cryptography.