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Friends Troubleshooting Network J. Wang*, Y. Hu§, C. Yuan*, Z. Zhang*, Y. Wang*. * Microsoft Research §U.C. Berkeley Presentation for course 20 ECES 728 by Kaushik Chowdhury OUTLINE Problem Definition Motivation PeerPressure – A Solution! Assumption & Design Considerations Protocol Details Attacks and Defences Experimental Results Motivation 17% of total cost of ownership = Configuration costs Windows registry/UNIX resource files Third party software Define “perfect” configuration Human time and effort Ownership Cost Peer-Pressure – A Solution! P( S ) 1 t P (V / S ) P( S / V ) P( H ) 1 1 t 1 m P (V / H ) c N P(V / S ) P( S ) P(V / S ) P( S ) P(V / H ) P( H ) FTN - Assumptions Friends contribute authentic/relevant/ non-privacy compromising information Recursive trust, not transitive trust Privacy through history less /futureless Random Walk Destination free searching/Routing FTN-Approaches Integration of Search & Aggregation ● Separate search step may return IP address of helpers ● Helps determine the applications running on Helper’s m/c ● Parameter value represents collective state History less & futureless Random-Walk ● No information is present on nodes covered or to-be covered ● The reply follows the same path back FTN-Protocol Design Step #1 Creating a request Remove all entries that contain usernames Form the “FTN REQUEST” Each request is identified with H(n,All Entry Names) FTN-Protocol Design…contd Step #2 Forward Path Aggregation Sick m/c establishes secured channel. Request is sent Friend replies with ACK/NACK Node becomes helper with probability Ph Friend Sick 4 REQ: Secured channel ACK: NACK: 5 FTN-Protocol Design…contd Use of Ph Second-last hop can infer last hop’s information Counter! Poll last hop with fake requests and then analyze statistically Solution: Bimodal Ph – Ph takes smaller value with small R R=1, e=0 R=0, e=1 FTN-Protocol Design…contd Last hop and Return Path If R=0, node waits for random amount of time, and then sends reply back Without random wait, previous node can launch polling attack Sick node subtracts random value initialization and performs Peer-Pressure diagnosis FTN - Challenges Compromised friends! Node remembers the value of R when the request message passed by Node forwards reply if: (a) (b) (c) Number of additional matches does not exceed R Count in value distributions does not decrease Sum of all counts in Reply – Sum of all counts in Request = R An Example FTN - Challenges Sybil Attack Malicious nodes collude in the attack Counter: Send multiple troubleshooting requests hoping that majority will return correct results The earlier a compromised node appears in the path, more is the damage High fan out thus reducing R Example of Sybil Attack R is large: One compromised node can bring in a host of others Countering Sybil Attack R is small: Need a larger fanout. Hence effect of compromised path can be avoided! Gossip Attack Ph + history less +futureless strategy can mitigate most attacks except one: Victim is between two gossipping friends, including sick friend Whenever victim ‘helps’ information can be inferred by the two gossipers Solution: Random Perturbation: Adding of a random noise than incrementing Results & Experimentation Peer Pressure could pin-point the root-cause misconfiguration in 12 out of 20 real-world troubleshooting examples Types of Suspects Related Work FreeNet : Distributed Anonymous Information Storage/Retrieval Crowds : Anonymous Web Transactions These require point to point communications & FTN is destination free Problem of privacy-preserving similar to secure/private voting Differences between voting Voters need to be authenticated by a centralized authority Participation privacy Voting requires precise vote tallies Other work like that in sensor networks involve identity revealing authentication if integrity of data is to be ensured.