Taxonomy of Trust Relationships in Peer-to-Peer (P2P)

Communication

Farookh Khadeer Hussain

, Elizabeth Chang

, Tharam Dillon

School of Information Systems

Curtin University of Technology

GPO Box U1987, Perth WA 6845, Australia

Faculty of IT

University of Technology, Sydney

Broadway, Sydney, NSW 2007, Australia

Abstract. Trust between two communicating peers is increasingly catching the

attention of the research community. Numerous trust models and trust

management protocols have been proposed to enable the task of establishing

trust between two communicating peers. In this paper, we enumerate all the

possible types of trust relationships between two peers in P2P communication,

with examples. Additionally, we discuss the conditions when a given trust

relationship between two peers is feasible.

1 Introduction

Trust has been analyzed from social and psychological perspectives [5] and has long

been a focal point of interpersonal relationships. Many of us use the word TRUST in

our daily lives. However, trust has different interpretations and different meanings in

different contexts and domains.

In the literature, Marsh was the first person to introduce the concept of trust in

computer science [4]. He introduced the notion of trust in distributed artificial

intelligence.

In this paper, we focus on the possible trust relationships in peer-to-peer

communication. We discuss the conditions under which a given trust relationship is

feasible. This paper is organized as follows; Section 1 is brief introduction to trust, in

Section 2 we present the various possible trust relationships and Section 3 is the

summary of this paper along with future work.

2 Trust Relationships in Peer-to-Peer (P2P) Communication

In this section we discuss with examples the various possible trust relationships in

peer-to-peer communication. In Section 2.1, we present a formal definition of what

Khadeer Hussain F., Chang E. and Dillon T. (2004).

Taxonomy of Trust Relationships in Peer-to-Peer (P2P) Communication.

In Proceedings of the 2nd International Workshop on Security in Information Systems, pages 99-103

DOI: 10.5220/0002661900990103

 SciTePress

we mean by a trust relationship. In Section 2.2 we discuss the various possible trust

relationships. We believe that the various possible trust relationships in P2P

communication are:

1. Implicit Trust Relationship

2. Mutual Trust Relationship

3. Group Trust Relationship

4. Federation Trust Relationship

2.1 Definition of Trust Relationship

We define a trust relationship as ‘a bond or association between the involved peer/s,

which signifies the trust between the involved peer/s’.

In this paper, we use the terms ‘person’ and ‘peer’ interchangeable because a

person is always behind a peer and a peer’s behavior depends directly on the person

controlling it.

2.2 Implicit Trust Relationship

We define the binding between a person and itself, which signifies the belief in its

capability or willingness to perform an action at a given point of time, as ‘Implicit

Trust Relationship’. We believe that implicit trust relationships depend on the

following factors:

• The capability or willingness of the person to perform a specific

action at a given point in time; and

• Whether the person is an optimist or a pessimist.

Some peers have the tendency to believe that they can do everything in this world

(optimists), while they may not necessarily be capable of doing it. In contrast, some

people may have a pessimistic attitude towards things and they tend to underrate their

capabilities (pessimists). We call this relationship of a given peer in itself that

signifies the trust that it has in itself to perform a specific action at a given point in

time as Implicit Trust Relationship. In implicit trust relationships, only one peer is

involved. Implicit trust relationships are a subset of all the rest of the trust

relationships.

2.3 Mutual Trust Relationship

We define the binding between a peer and another peer, which signifies the belief in

the other peer’s capability or willingness to perform an action at a given point in time,

as a ‘Mutual Trust Relationship’. This is the most common form of trust relationships

in P2P communication. In mutual trust relationships, there are exactly two peers who

are bound by the trust relationship. We believe that implicit trust relationships

depend on the following factors:

• The capability or willingness of a peer to perform a specific action at

a given point in time , as perceived by another peer;

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• The psychological type of the peers involved in the mutual trust

relationship [2, 3];

• The outcome of the previous interactions between the peers in the

mutual trust relationship; and

• The degree of the trust recommended by the intermediate peer [1].

2.4 Group Trust Relationships

We define a group of peers as ‘a collection of more than two peers who perform a set

of coherently related tasks and each peer in the group trusts every other peer in the

group, for a given context, at a given point in time’.

We define the binding between a peer and another peer/s, belonging to the same

group, which signifies the belief the other peer’s capability or willingness to perform

an action at a given point in time as ‘Group Trust Relationship’.

Unlike mutual trust relationships, group trust relationships can involve two or more

than two peers. The peers, however, must belong to the same group which is not the

case in mutual trust relationship.

We feel that trust relationship between two peers who belong to the same group is

a group trust relationship and not a mutual trust relationship. Additionally, we believe

that just like trust, groups are formed for a specific context. Two peers who are

members of a group for a specific context may or may not be members of same group

for another context.

For example consider the following scenario:

Let us assume that we have a set of peers A1, A2, A3, A4 …..A10. Each peer

trusts the other peer for its authenticity at a given point in time. This set of peers

A1……A10 is said to form a group where every peer in the group trusts the

authenticity of the other members of the group. The trust relationship between A1

and A3 is an example of group trust relationship and not mutual trust relationship.

If A11, which is a new peer, joins this group and all the members in the group trust

A11 for its authenticity, then A11 becomes a member of the group for that context.

2.5 Federation Trust Relationships

For defining ‘Federated Trust Relationships’, we need to first define and explain what

we mean by Federated P2P Communication. We define Federated P2P

Communication as the communication that takes place between two or more than two

groups of peers.

As we mentioned in Section 2.4, the members in each of these groups are centered

on a set of coherent interest/s and the peers belonging to a group perform a specific

task. In Federated P2P Communication, a peer acts on behalf of the group to which it

belongs. If two peers are communicating with each other, it is analogous to two

distinct groups communicating with each other. The communication between the

groups of peers is regarded as Federated P2P Communication.

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We define ‘Federated Trust Relationships’ as the binding between two or more

than two distinct groups of peers which signify the peer group’s belief in the peer

group’s capability or willingness to perform an action at a given point in time.

A peer in a federated P2P communication may be a member of more than one

group. We strongly believe that this is the way that P2P communication will be

organized in the future.

For example, let us consider a peer-to-peer file-sharing application, Gnutella.

Users of Gnutella can share files with each other. Users may share files like music

files, educational documents, documents related to politics etc. Each of these types of

files forms a different domain of interest. These domains of interest can be further

subdivided. For example, some users who are members of the group which shares

music files may be interested in sharing just English songs and not songs composed in

any other language. Similarly, some users who are members of the group that shares

political documents may be interested in documents related to a particular

country/group. A group, as explained above, is formed by a set of peers who have a

coherent interest. A peer can join and leave the group at will. Groups can be formed

dynamically and destroyed dynamically. Peers can join any group and leave any

group.

Let us assume that there are two groups Group A and Group B as shown below.

Let us further assume that Peer A and Peer B belong to Group A and Peer C and Peer

D belong to Group B.

Let us assume that Peer A who belongs to Group A, wants to interact with Peer C

of Group B. The binding between Peer A and Peer C, an example of the federated

trust relationships and the communication between them is an example of federated

P2P communication

The binding between Peer A and Peer B or the binding between Peer C and Peer D

is an example of group trust relationships.

The proposed federated P2P communication structure has all the features that

should be present for a P2P communication. We believe that in the future P2P

communication will be organized in this way, because a given document can be found

with much ease, with less usage of bandwidth as can be found in non-federated P2P

communication. In non-federated P2P communication, to locate a particular

document, the search query is broadcast to the whole network thus resulting in

inefficient use of bandwidth. In federated P2P communication, the query is broadcast

only to the members of the group thus leading to a far more efficient use of

bandwidth. If a peer is a member of more than one group, the query is broadcast to

the group, which has the maximum probability of answering the query. We believe

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that federation trust relationships may exist between two, or more than two, groups of

peers.

References

1. Hussain, F.K., Chang, E. & Dillon,T.S., ‘A methodology for reputation

management in peer-to-peer (P2P) communication’. (Working Paper)

2. Hussain, F.K., Chang, E. & Dillon, T.S., 2004, ‘Factors of trust that affect

trustworthiness in peer-to-peer (P2P) based e-commerce’, Proceedings of the

International Conference of Business and Information, Taiwan.

3. Hussain, F.K., Chang, E. & Dillon, T.S., 2004, ‘Classification of trust in peer-to-

peer (P2P) communication’, International Journal of Engineering Intelligent Systems,

vol. 12.

4. Marsh, S., 1994, ‘Formalizing trust as a computational concept’, University of

Stirling, UK.

5. Smith, J.H., 2002, ‘The architectures of trust’, Faculty of Humanities, Copenhagen,

University of Copenhagen.

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