A few comments:
import sun.misc.*; Don't do this. It is non-standard and not guaranteed to be the same between implementations. There are other libraries with Base64 conversion available.
byte[] encVal = c.doFinal(Data.getBytes()); You are relying on the default character encoding here. Always specify what character encoding you are using: byte[] encVal = c.doFinal(Data.getBytes("UTF-8")); Defaults might be different in different places.
As @thegrinner pointed out, you need to explicitly check the length of your byte arrays. If there is a discrepancy, then compare them byte by byte to see where the difference is creeping in.
