> 3. Add 3 bytes of padding, set to zero, to the encrypted section just > before the IP header, marked for future use. > Pros: satisfies IETF mantras, can use those extra bits in the future > for interesting protocol extensions for authenticated peers. > Cons: lowers MTU, marginally more difficult to implement but still > probably just one or two lines of code. I'm not a crypto expert, but does this not give you a helping hand in breaking the crypto? You know the plain text value of these bytes, and where they are in the encrypted text. Andrew