05-10-2010 06:50 PM - edited 05-10-2010 06:52 PM
Take a look at "net.rim.device.api.crypto.CryptoInteger" it requires Certicom signing but if you got your keys within the last couple months you should be good.
If you don't have Certicom signing keys then send an email to RIM, since they own them now they will give them to you. Just search the forums for where to email them.
EDIT: You can also try "CryptoByteArrayArithmetic" but the same signing requirement as above is there.