  In this paper, a novel and efficient hardware implementation of
steganographic cryptosystem based on a public-key cryptography is proposed.
Digital images are utilized as carriers of secret data between sender and
receiver parties in the communication channel. The proposed public-key
cryptosystem offers a separable framework that allows to embed or extract
secret data and encrypt or decrypt the carrier using the public-private key
pair, independently. Paillier cryptographic system is adopted to encrypt and
decrypt pixels of the digital image. To achieve efficiency, a proposed
efficient parallel montgomery exponentiation core is designed and implemented
for performing the underlying field operations in the Paillier cryptosystem.
The hardware implementation results of the proposed steganographic cryptosystem
show an efficiency in terms of area (resources), performance (speed) and power
consumption. Our steganographic cryptosystem represents a small footprint
making it well-suited for the embedded systems and real-time processing engines
in applications such as medical scanning devices, autopilot cars and drones.
