I imagine a sort of device where you have a private key stored on some chip that you plug into a handheld device. All the device does is take in bytes from a se

I imagine a sort of device where you have a private key stored on some chip that you plug into a handheld device. All the device does is take in bytes from a serial port and output the decrypted content out another serial port. Then you can make sure that your decrpyted contents only ever exist on a non-network connected computer. Or better yet, only view or manipulate the decrypted content from a laptop with read only storage (e.g. booting into linux from a dvd).