A. RSA Algorithm
In this paper, we use the RSA public key cryptosystem,
which is the first public key algorithm which can be used in
digital encryption and digital signature [5]. It has the
advantages of easy to understand and easy to operate. The
mathematical theory of RSA algorithm is based on a composite
number with large number factors is decomposed into two
prime numbers is very difficult. In this paper, we use the digital
signature system of RSA to authenticate and strengthen
security. We should first sign and then encrypt in the
realization process [6].