Suppose an intermediate node for onion routing were malicious, exposing the sour
ID: 3766593 • Letter: S
Question
Suppose an intermediate node for onion routing were malicious, exposing the source and destination of communications it forwarded. Clearly this disclosure would damage the confidentiality onion routing was designed to achieve. If the malicious node were one of two in the middle, what would be exposed. If it were one of three, what would be lost. Explain your answer in terms of the malicious node in each of the first, second, and third positions. How many nonmalicious nodes are necessary to preserve privacy?
Explanation / Answer
Onion routing:
Onion routing is a technique for anonymous communication over a computer network.
In onion routing the sender and receiver remains anonymous because each intermediary knows only the location of the immediately preceding and following nodes.
If malicious node is one of the two then
case 1: First node is malicious node.
Then this node discloses source.
So, second node knows source.
second node also knows the destination as it is the last node.(No preservetion of privacy)
case 2: second node is malicious in this case.
first node knows the source.
Second node knows destination.
In this case second node discloses destination.
So first node knows both source and destination.(No preservetion of privacy)
If malicious node is one of three.
case 1: First node is malicious node.
Then this node discloses source.
Third node knows destination.
It also knows the source because of first node.(No preservetion of privacy)
case 2: second node is malicious in this case.
only first node knows source and third node knows destination.
second node knows nothing about source and destination.
first node knows nothing destination.
third node knows nothing about source.(privacy is preserved)
case 3: Third node is malicious node.
It discloses destination.
as first node already know source and now it knows destination because of third node.(No preservetion of privacy)
The node after the source and the node before the destination should be nonmalicious to preserve privacy.