Structural Feature Based Anomaly Detection for Packed Executable Identification - Computational Intelligence in Security for Information Systems - page 240

2 Produre

In this section, first, we introduce our model of location tagging system in Section 2.1
which also includes model of location tags and location exposure policy. In Section
2.2, we mainly describe the working process of Produre. In Section 2.3 and Section
2.4, we describe algorithm for users' credibilities and issues about key management to
supplement Section 2.2.

2.1 Location Tagging System

Location Tag Model. In traditional tagging system, users annotate tags to resources in
the system to show their subjective feelings about the resources. In this paper, we define
a location tag [3] as an ephemeral, unpredictable nonce associated with a location and
can be derived from various electromagnetic signals available in the environment, such
as WiFi and Bluetooth. It can be thought of as a shared pool of entropy between all
users at a given location at a given time. A location tag lt can be represented as follows:

lt = u, l, t (1)

where
- u : the user who sends the location tag lt , i.e., the annotator of the location tag.
- l : the location of user u when he is sending the location tag lt , which is the main
content of the location tag. Apparently, there may be more information in a location
tag due to different kinds of location services and in this paper we just extract
several main items to design Produre.
- t : the time when the location tag lt is sent, which means at the time of t ,user u is
in the location of l .

System Model. We d e fi n e a location tagging system (say S lt ) as a system which pro-
vides location services according to location tags. We also define the user who raises
a proximity discovery request as a “client”. The system model which meets the design
requirement of Produre is given as follows:

S lt = U,LT,C,K (2)

where

- U : the set of users in the tagging system, among whom there are friendship relations
because of introducing online social network.
- C : the processing center of the whole system, which is in charge of communication,
computation, and storage of friendship relations between users and their location
exposure policies.
- LT : the set of location tags in the system. Users in the system repeatedly send
location tags to the processing center.
- K : the key management center. It is responsible for generating public and private
key pairs for the processing center and each user in the location tagging system,
maintaining and destroying the public and private key pairs when necessary.