I am not sure if you are using the right way . you may check the J2EE
templates for one or other ways that you may do that more effective.

As a short term solution you can encrypt the parameter values using a
server encryption key on the provider and decrypt it on the consumer
side.
In order to Encipher, decipher the strings you have different
alternatives. From simple own written classes that "Xors" the bytes to
deploying Public key cryptography algorithms using a JCA/JCE provider.

Xor way :

original-byte xor key = transmission-byte
transmission-byte xor key = original-byte

JCA/JCE Way:

read and get yourself informed about the java  security architecture. the
class you will use ( assuming you have a security provider
implementation deployed in your server framework) is
java.sun.com/.../Cipher.html