Information Technology Reference
In-Depth Information
c = 1 - u x
(5)
where: r is amount of positive evidence; s is amount of negative evidence; t is total
evidence given as t=r+s ; c or c(t ) or c(r, s ) is certainty as a function of total
evidence; and f is distance of focus to the centre of an ellipse formed by mapping
the positive and negative evidence to major and minor semi-axes of an ellipse.
Fig. 2. Trust Engine
The opinion formed by the monitors is combined with the opinion formed based on
the enterprise user's feedback and complaints. The subjective logic by Josang [7] is
used to combine multiple opinions to form a single opinion using the operators
such as conjunction, consensus that allows performing logical operations on
opinions. This paper uses the opinion model proposed in [13] and the subjective
logic operators [7]. The conjunction operator is standard logic “AND” operating on
the opinions. The consensus operator enables combining the opinions of entity A
and entity B representing an imaginary entity [A,B]'s opinion about proposition x .
iii. Reputation: The probability expectation of an opinion is used to provide the
reputation rating. The expectation of an opinion is given as E(w(x))=b+au where
E(w(x)) Є [0,1] and a(x) is base rate that provides the weight of uncertainty that
contributes to the probability expectation.
Figure 2 shows process of modeling the security reputation by broker. The first
step is the broker getting evidential information from two sources a) Monitor and b)
Customer interface. The second step is to convert the evidence obtained to compute
an opinion. The third step is to calculate the reputation of a service provider based on
the opinion formed. The details of reputation calculation are given in section 4.
4
Reputation System
The reputation of a cloud service provider is calculated in terms of its
trustworthiness(T) using opinion obtained from computations, namely i) Incidence
Monitoring(M) : Security incedence events received from monitoring ii) Enterprise
User Rating(EUR) : Ratings provided by the enterprise user for satisfaction of the
Search WWH ::




Custom Search