Recently, a novel public-key cryptosystem constructed on number fields is presented. The prominent theoretical property of the public-key cryptosystem is a quadratic decryption bit complexity of the public key, which consists of only simple fast arithmetical operations. We call the cryptosystem NICE (New Ideal Coset Encryption). In this paper, we consider practical aspects of the NICE cryptosystem. Our implementation in software shows that the decryption time of NICE is comparably as fast as the encryption time of the RSA cryptosystem with e = 2¹⁶+1. To show if existing smart cards can be used, we implemented the NICE cryptosystem using a smart card designed for the RSA cryptosystem. Our result shows that the decryption time of NICE is comparably as fast as the decryption time of RSA cryptosystem but not so fast as in software implementation. We discuss the reasons for this and indicate requirements for smartcard designers to achieve fast implementation on smartcards.