I want to perform H(number) xor username operation for my academic project..can anyone please help me??and tell me how to concatenate integer with string????

I have created three nodes with transmission range 100 and interference range 450, called n0, n1, and n2. n0 cannot communicate with n2, so first n0 must authenticate n1 so that n1 can communicate with n2. My problem is how to create ID and password for nodes, and I need to perform h(ID) and Xor with key? Could you please help me?

I want to develop this whole concept in java.in case if it is not possible tell me how to hash a string...