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Traditionally, it has been difficult to deploy mobile Java security in mass market mobile devices primarily due to size and speed constraints. NTRU, a relatively new public key cryptosystem based on the shortest vector problem in a lattice, with many advantages compared with other cryptosystems, such as high speed and low memory use, provides the possibility to overcome the constraints. This paper briefly describes NTRU cryptosystem and two approaches to optimize the algorithm, such as changing forms and using low hamming weight products; the former approach simplifies both the key generation and the decryption, and the latter one increases the speed of the convolution multiplication by nearly 2 times. Experiments on the performance of enhanced NTRU-251 compared with RSA-1024 in the mobile Java device are made. Preliminary experimental results show the advantages of NTRU over RSA, such as, at the similar security level, the key size of NTRU is less than a quarter of that of RSA, and the speed of NTRU is much faster than that of RSA; the key generation is more than 200 times faster, the encryption is almost 3 times faster, and the decryption is about 30 times faster. These experimental results show the applicable prospect of NTRU in mobile Java systems.