- Other VPNs
Verify the statements concerning bit flipping in stream ciphers. Specifically, show that exclusive-ORing a 1-bit into the ciphertext changes the corresponding plaintext bit.
Would it make sense to reverse the L2TP/IPsec encapsulation? That is, what would be the advantages and disadvantages of establishing an IPsec connection between a host on a remote network and a server on the enterprise network, and then running that through an L2TP tunnel between the LAC and LNS? The topology would be similar to that in Figure 5.3, but IPsec would be encapsulated in L2TP messages instead of the other way around.
Make the argument that a VPN is more secure than a leased line.
Given a VPN with robust cryptographic primitives and protocols, or a dedicated leased line, what are the most vulnerable points in the network? That is, if a malefactor were tasked with compromising the network's data, how should the attacker proceed?