fix Bouncy Castle lib can't not using on android.
Why?
The Android platform unfortunately ships with a cut-down version of
Bouncy Castle - as well as being crippled, it also makes installing an
updated version of the libraries difficult due to classloader conflict

Spongy Castle is the stock Bouncy Castle libraries with a couple of
small changes to make it work on Android:

all package names have been moved from org.bouncycastle.* to
org.ripple.bouncycastle.* - to avoid classloader conflicts
also refer to http://rtyley.github.io/spongycastle.