PPP link encryption?

[Alexandra Griffin <acg@mandrake.cen.ufl.edu>]

Is there any software out there on the net for doing real-time,
transparent encryption of a PPP link?

Also, if this link is running at 600kbit/s to 1Mbit/s, how much
processing power would be required to keep up (assuming we're using,
say, the IDEA cipher)?  Would a dedicated 386DX/33-based router on
each end be sufficient?

Finally, could someone make a ballpark estimate as to the amount of
additional latency that would be added?

thanks,
- alex