An all-printed physically unclonable function based on a single-walled carbon nanotube network. The network may be a mixture of semiconducting and metallic nanotubes randomly tangled with each other through the printing process. The unique distribution of carbon nanotubes in a network can be used for authentication, and this feature can be a secret key for a high level hardware security. The carbon nanotube network does not require any advanced purification process, alignment of nanotubes, high-resolution lithography and patterning. Rather, the intrinsic randomness of carbon nanotubes is leveraged to provide the unclonable aspect.