1. Assume that passwords have length six and all alphanumerical characters, upper and lower case, can be used in their construction. How long will a brute force attack take on average if: l it takes one-tenth of a second to check a password? l it takes a microsecond to check a password? 2. How would you protect a tty device from other users? 3. The ARP (Address Resolution Protocol) associates hardware addresses with IP addresses. This association may change over time. Each node in the network keeps an ARP cache of corresponding IP and hardware addresses. Cache entries expire after a few minutes. A node trying to find the hardware addresses for an IP address that is not in its cache broadcasts an ARP request that also contains its own IP and hardware address. The node with the requested IP address replies with its hardware address. All other nodes may ignore the request. What is the scope for spoofing in the ARP protocol? Which defenses can be used against spoofing?