CS8803 Course Reading Summaries 
Title: Search and Replication in Unstructured

Peer-Peer Networks. 
 

Strengths:
-	The paper seems to be the first at 

time of publication in understanding the 

properties of 

scalable search algorithms, replication 

methods 

and network topologies for decentralized 

unstructured peer to peer network. 

-	The paper puts forward three critical 

yet essential properties i.e. 1) adaptive 

termination, 2) minimizing message duplication 3) 

small granularity of coverage. Using these three 

properties as a basis, the algorithms of 

Expanding Ring and K-Walker are presented. 

This allows the user to evaluate all the different 

kinds of algorithms using the same standard set of 

properties. 

-	The paper presents simulation for 

the new 

methodologies proposed by the authors in 

search 

and replication. For example, in Section 

2.3 the 

flooding of the network in Gnutella does 

not satisfy

 any of the three above mentioned 

properties and 

does not scale well. The expansion ring 

approach is

 significantly better than flooding by 

using adaptive 

termination while K-Walker is the best 

as it reduced 

the granularity of coverage. These 

simulations are a 

fundamental strength of the paper, as 

the authors have 

not only presented the new algorithm 

methodology but

 proof (simulation) that they are significantly 

better in reducing flooding. 

Weakness:
-The paper only uses 4 topologies mentioned in 

section 2 of the paper with an average of only 

4000 nodes per topology. In reality on the actual 

Internet, there are P2P nodes of a higher magnitude 

with heterogeneous topologies where K-Walker search 

techniques may not be scalable. 

-The paper does not model the various search 

algorithms with certain network topologies and study

 them analytically. 

-It would be interesting if the paper had 

presented the tradeoff between the two metrics in a 

distributed system of Square Root replication 

(minimizes search size) and Proportional replication 

(optimizes balance load). 

 - It is an excellent research for unstructured

 search and replication, but the paper must have 

presented statistics in comparing the three kinds 

of P2P i.e. Centralized, Decentralized (Structured)

 and Decentralized Unstructured in order to gauge

 whether in practice K-Walker search and the new 

replication methodology will make a significant 

difference if the number of people using this kind 

of P2P is relatively small. 

CS8803 Course Reading Summaries 
Title: TrustMe: Anonymous Management of Trust 

Relationship in Decentralized P2P Systems. 

Strengths:
 -The paper attempts to answer two important 

questions i.e. 1) Where should the trust value 

be stored? 2) How to securely access other peer's 

trust value. Question 1 is challenging enough, 

because of the decentralized nature of the Peer-Peer

 network. The paper explicitly lays out the questions

 it will attempt to answer ensuring the following 

properties remain invariant a) Security b) Reliability 

c) Accountability. This clear and concise scope and

 objective of the paper allows the reader to understand 

the context of the material to follow in the paper. 

- The paper solves the problem of storing user 

ratings as mutual anonymity. If nobody knows who 

the trust store is (including the peer whose trust

 value is being stored), there is hardly a chance 

that the trust store will be attacked.

-The paper highlights some of the shortcomings 

of Eigenrep such as Insecure Communication, DHT 

Threats, No Anonymity and Group Threats and at the 

same time TrustMe is resistant to these threats as

 it employs a random assignment of Trust Holding 

Agent peers and uses Public Key mechanism to prevent

 loss of anonymity. This reasoning allows the user

 to understand how TrustMe fairs and ranks with its 

competitors. 

-There are various challenging issues that need to

 handled e.g. how to select good trust stores, 

how to access ratings from them without knowing

 who/where they are? TrustMe provides all the 

answers.

-Section 3.3.2 presents some of the common attack 

scenario such as �Manipulating Reply Message�,

�Manipulating Proof of Interaction Messages� and how

 TrustMe maintains security, reliability and 

accountability. 


Weakness:
-One apparent weakness of the paper, is that in

 the user based approach a potential malevolent 

user can harmfully/intentionally harm a user 

providing good (QOS) by giving it low ratings. OR a

 group of malicious users together harm a good QOS

 provider. How will TrustMe address this?

-The trust value should be only visible for a user

 after it has received certain number of trusts. 

This is because, if a user receives a bad/low rating

 out of 1 users, then it has a 100% low rating. 

The paper should address this and use some sort of 

statistical/variance method to delete off votes that

 have large variance. 

-As security is cornerstone of TrustMe, 

the paper should have explored various other 

cryptographic methodologies that can be more 

efficient as compared to Public Key cryptography.