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 |
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} |
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} |
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 |