1. Trustworthy Distributed Search and Retrieval over the Internet
Presented by Yung-Ting Chuang
Research conducted in collaboration with
Isai Michel Lombera, Louise E. Moser and P. M. Melliar-Smith
Supported in part by NSF Grant CNS

2. Overview iTrust Introduction Implementation of iTrust
Performance evaluation
Conclusion and future work
WORLDCOMP’ iTrust Yung-Ting Chuang

3. iTrust vs Centralized Search Engine
Nowadays we use centralized search engines (Google, Yahoo, Bing, etc)
Benefits
Drawbacks
iTrust – distributes metadata and request to random participating nodes
WORLDCOMP’ iTrust Yung-Ting Chuang

4. Distribution of Metadata
Source of
Information
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5. Distribution of a Request
Source of
Information
Request
Encounters
Metadata
Requester of
Information
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6. Retrieval of Information
Source of
Information
Request
Matched
Requester of
Information
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7. iTrust Implementation
WORLDCOMP’ iTrust Yung-Ting Chuang

8. Web Server Foundation
cURL - inter-node communication and resource-specific actions
Follows HTTP redirects
SQLite - stores node, metadata, membership, and resources
Rapid deployment
Minimal local write privilege
Constrains enforcement
Session module - tracks and distinguishes users
Log module – for debugging and simulation
PECL - inter-node search and requests
Send POST statement
WORLDCOMP’ iTrust Yung-Ting Chuang

9. Application Infrastructure
Metadata functions XML
Senders: scan the resources and creates an XML list
Receivers: scan and insert sources into current node
Helper functions:
Inserts nodes into the membership
Insert keywords into the database
Upload or fetch resources
Node querying
Java jar files
Apache Tika packages
Apache Lucene packages
WordNet dictionary
WORLDCOMP’ iTrust Yung-Ting Chuang

10. Public Interface Computer interfaces Human interfaces
Handles inter-node communication (ex. queries,
resource distribution, and metadata list distribution)
Use inbox-type fashion to distribute/read request.
Human interfaces
Add nodes or metadata keywords
Generates requests
Provide feedback
WORLDCOMP’ iTrust Yung-Ting Chuang

11. Prototype Implementation of iTrust
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12. Prototype Implementation of iTrust
WORLDCOMP’ iTrust Yung-Ting Chuang

13. Prototype Implementation of iTrust
* Explain what’s the meaning of “hit” and scoring.
WORLDCOMP’ iTrust Yung-Ting Chuang

14. Performance Evaluation
Assume:
All nodes have the same membership set
Internet is reliable
All nodes has enough memory to store sources
Variables:
Membership contains n participating nodes
Metadata are distributed to m nodes
Requests are distributed to r nodes
Proportion x of participating nodes are operational
WORLDCOMP’ iTrust Yung-Ting Chuang

15. Probabilistic Analysis
Probabilities:
1st node has the metadata and is operational: mx
No match on 1st trial: 1- mx = n-mx
No match on 2nd trial: n-mx-1
No match on rth trial: n-mx-r+1 n n n
n-1
n-r+1
WORLDCOMP’ iTrust Yung-Ting Chuang

16. Probabilistic Analysis
Probability q of no match on r trials:
q = n-mx n-mx-1 … n-mx-r+1
n n n-r+1
Probability p of a match on r trials:
p = 1 - n-mx n-mx-1 … n-mx-r+1 , where
If mx+r > n, then p = 1
n ≥ mx+r
WORLDCOMP’ iTrust Yung-Ting Chuang

17. Simulation Results
libCURL - URL transfer library for transferring data
Steps our program performed:
Clears database
Adds nodes
Uploads a file and creates metadata
Distributes metadata
Selects nodes for requests at random
If at least one node replies, program returns 1; Else program returns 0
WORLDCOMP’ iTrust Yung-Ting Chuang

18. Performance Evaluation Results
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19. Performance Evaluation Results
WORLDCOMP’ iTrust Yung-Ting Chuang

20. Conclusion and Future Work
Achieve high probability of match
Match remains high even some nodes are subverted
We plan to evaluate the effectiveness, efficiency, scalability, and reliability in PlanetLab
We are investigating possible attacks on iTrust and countermeasures to such attacks
We are investigating other implementations of iTrust based on SMS
We plan to make the iTrust source code, tools, documentation, freely available
WORLDCOMP’ iTrust Yung-Ting Chuang

21. Questions? Comments? Our iTrust website:
Contact information:
Yung-Ting Chuang:
Isai:
Our project is supported by NSF: CNS
WORLDCOMP’ iTrust Yung-Ting Chuang