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revision 1.99 by hemppah, Fri Feb 28 14:42:46 2003 UTC revision 1.100 by hemppah, Mon Mar 3 08:47:01 2003 UTC
# Line 285  performance increases signficantly. As a Line 285  performance increases signficantly. As a
285  structured Peer-to-Peer systems have adopted this method with some modifications  structured Peer-to-Peer systems have adopted this method with some modifications
286  \cite{gnutella2url}, \cite{shareazaurl}, \cite{fasttrackurl}, \cite{morpheusurl},  \cite{gnutella2url}, \cite{shareazaurl}, \cite{fasttrackurl}, \cite{morpheusurl},
287  \cite{kazaaurl}, \cite{jxtaurl}, \cite{jxtaoverview}, \cite{botros01jxtasearch},  \cite{kazaaurl}, \cite{jxtaurl}, \cite{jxtaoverview}, \cite{botros01jxtasearch},
288  \cite{ganesan02yappers}, \cite{kato02gisp}.  \cite{ganesan02yappers}.
289  Figures \ref{fig:gnutella_overlay_supernodes} and \ref{fig:gnutella_overlay_cluster}  Figures \ref{fig:gnutella_overlay_supernodes} and \ref{fig:gnutella_overlay_cluster}
290  illustrated two possible variations of power-law overlay networks. All the systems  illustrated two possible variations of power-law overlay networks. All the systems
291  share the property of that high degree peers maintain index of all other peers  share the property of that high degree peers maintain index of all other peers
# Line 972  Peernet Line 972  Peernet
972    
973  \chapter{Open Problems in Peer-to-Peer}  \chapter{Open Problems in Peer-to-Peer}
974    
975    In this chapter, we discuss open problems in Peer-to-Peer domain. We describe
976    open problems and their proposed solutions. Then, we list all issues in
977    tables; we list description of the problem, solution and comments on that
978    specific open problem. Note that open problems list considered here is not meant
979    to be an exhaustive survey of \emph{all} open problems in Peer-to-Peer domain;
980    we focus our attention to security, scalability and performance related issues
981    only.
982    
983    \section{Overview}
984    
985    Partly due to the non-maturity of modern Peer-to-Peer technology, it has several
986    open problems to be solved. Main open problems are related to performance, scalability
987    and security. More important, many techniques developed for traditional distributed
988    systems may no longer apply with Peer-to-Peer systems. Therefore, new solutions are
989    needed to make Peer-to-Peer systems more secure and efficient.
990    
991    Both loosely structured and tightly structured approach have their own main problems.
992    Since Napster \cite{napsterurl} and Gnutella \cite{gnutellaurl} was first time introduced
993    to public, researchers' main concern has been scalability problem of loosely structured
994    approach. However, people often misunderstand the scalability problem of loosely structured
995    approach; loosely structured approache's \emph{network} is scalable, but the \emph{query model} is not
996    scalable. Tightly structured approach's main concern is to make overlay's data lookup
997    routing more flexible againts hostile attacks. Another key problems in tightly structured
998    approach are the lack of keyword searches and support for heterogeneous peers.
999    
1000    To make Peer-to-Peer systems even more popular (e.g., in industry), Peer-to-Peer domain
1001    needs better infrastructures to deal with security issues. There has been done some
1002    research regarding anonymity, access control, data availability and data integrity. However,
1003    more research is needed specifically with redundancy, robustness and entity identification.
1004    
1005    
1006  \section{Security problems in Peer-to-Peer}  \section{Security problems in Peer-to-Peer}
1007    
1008    In this section we discuss security problems related to Peer-to-Peer domain.
1009    
1010  \subsection{Attacks}  \subsection{Attacks}
1011    
1012    There are five well known attack models againts Peer-to-Peer systems: Sybil attack \cite{douceur02sybil},
1013    Fail-stop attack, Spam attack \cite{naor03simpledht}, Byzantine problem \cite{357176} and \cite{296824}, and
1014    general Distrubuted Denial of Service attack.
1015    
1016    In Sybil attack model, hostile entity presents multpile
1017    entities. Therefore, one hostile entity can control a large fraction of the Peer-to-Peer system. The best
1018    possible solution to Sybil attack would be that system could \emph{distinct} entities reliably. Unfortunately,
1019    currently there no realizable techiques for this task. Partial solutions for Sybil is attack is to replicate
1020    and fragment data randomly among several participating peer. However, both suggestions assume that two different
1021    remote entities are actually different; Sybil attacks are still possible and therefore, would need centralized
1022    authority for reliable authentication. As author arques in \cite{douceur02sybil}, without centralized authority,
1023    Sybil attacks are always possible in Peer-to-Peer system except under extreme and unrealistic assumptions of
1024    resource parity and coordination among entities.
1025    
1026    
1027    
1028    1) Sybil attack \cite{douceur02sybil}
1029    2) Fail-stop
1030    3) Spam generating model \cite{naor03simpledht}
1031    4) Byzantine problem \cite{357176}, p2p domain \cite{296824}
1032    5) General DDoS
1033    
1034    
1035    
1036  1) Sybil attack \cite{douceur02sybil}  1) Sybil attack \cite{douceur02sybil}
1037  2) Fail-stop  2) Fail-stop
1038  3) Spam generating model \cite{naor03simpledht}  3) Spam generating model \cite{naor03simpledht}
# Line 1002  b) Could multi-butterflier be used in an Line 1059  b) Could multi-butterflier be used in an
1059  c) Are there lower bounds for average degree of nodes, query path length etc. for a network that is  c) Are there lower bounds for average degree of nodes, query path length etc. for a network that is
1060  fault tolerant to linear number of adversial faults ?  fault tolerant to linear number of adversial faults ?
1061    
 Solutions for Sybil Attack:  
 1) data replication among several peers  
 2) data fragmentation among several peer  
   
 BUT:  
 -in either case, both approaches assumes that two different remote entities are actually different; sybil attacks are still possible --> need for centralized authority  
 -in p2p environment, trusting to collective assurance of multiple signatories (like PGP) is not safe/undermines the authenticity of system (because of sybil attacks)  
 -\cite{douceur02sybil} argues that Sybil attacks are always possible except under extreme and unrealistic assumptions of resource parity and coordination among entities  
1062    
1063    
1064  \subsection{Data authenticity and integrity}  \subsection{Data authenticity and integrity}
# Line 2125  blocks \emph{directly} from the network. Line 2174  blocks \emph{directly} from the network.
2174  database systems may prove to be useful. However, more research is needed  database systems may prove to be useful. However, more research is needed
2175  in this area.  in this area.
2176    
2177    \cite{kato02gisp}
2178    
2179  In the following months, we will implement a working Storm Peer-to-Peer  In the following months, we will implement a working Storm Peer-to-Peer
2180  prototype. Potential candidates for tightly structured overlays are  prototype. Potential candidates for tightly structured overlays are
2181  Kademlia \cite{maymounkov02kademlia}, Koorde \cite{kaashoek03koorde} and  Kademlia \cite{maymounkov02kademlia}, Koorde \cite{kaashoek03koorde} and

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