  Modern mobile phones are increasingly being used for more services that
require modern security mechanisms such as the public key cryptosystem RSA. It
is, however, well known that public key cryptography demands considerable
computing resources and that RSA encryption is much faster than RSA decryption.
It is consequently an interesting question if RSA as a whole can be executed
efficiently on modern mobile phones. In this paper, we explore the efficiency
on modern mobile phones of variants of the RSA cryptosystem, covering CRT,
MultiPrime RSA, MultiPower RSA, Rebalanced RSA and R Prime RSA by comparing the
encryption and decryption time using a simple Java implementation and a typical
RSA setup.
