11 Information Hiding for Spatial and Geographical Data
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the modeling and security of public-key steganography systems [1, 2]. However, to
the best of our knowledge, the use of this technique in conjunction with digital mapping is a novel application.
11.6 A Proposal for a Steganography GIS Model
In technical terms, public-key steganography is employed to realize a GIS that allows
authorized users to have access to secret information. The basic idea is that potential
users u i are associated with a couple of secret-key and public-key, < S K i , PK i >, that
are employed to exchange information with the other entities. The secret information
is embedded in the digital map with the public-key of the authorized users. Then, the
digital map may be delivered to all the users. However, the hidden content can be
extracted only by those users that own the corresponding secret-key that is used to
extract this information.
The main advantage of this approach is to convey different levels of strategic information in an innocuous way without raising suspicion in other potential users who
cannot be authorized to access some kind of information. In the scenario of a public
channel this solution is more appropriate than the use of cryptographic mechanisms
because encrypted content can easily be recognized. On the other hand, steganography content is indistinguishable from other content that does not contain hidden
information inside. In terms of security, one important requirement is the confidentiality of sensitive information.
Figure 11.5 shows the diagram of a GIS employing public-key steganography
to make sensitive content available only to authorized people. In the following, we
describe the functionality of this approach. As illustrated in Fig. 11.5(a), the sensitive
information (hidden content) is embedded in the digital map with the public-key PK i
of the potential users class u i . This produces a stego-map that can be visualized
differently according to the users that receive it. In fact, as illustrated in Fig. 11.5(b),
users visualize the stego-map by applying the extraction application. The extraction
application is composed of two extraction functions: Extract DM () and Extract HC ().
By applying the Extract DM () function, users retrieve the public digital map (cover).
By applying the Extract HC () function, users that own the corresponding secret-key
S K i are able to retrieve the hidden content, while users that do not own the right
secret-key are unable to notice any hidden content in the stego-map.
The embedding and extraction functions are illustrated in Table 11.2. A detailed
description of these functions is given in the following sections. Our aim is to provide
a GIS conceptual model that employs public-key steganography. We do not address
technical details about the implementation of this model, including, for example, the
number of GIS users or the possibility to employ multiple public-keys per user. Such
details strongly depend on the specific scenario; however, this issue goes outside the
scope of the chapter.
251
the modeling and security of public-key steganography systems [1, 2]. However, to
the best of our knowledge, the use of this technique in conjunction with digital mapping is a novel application.
11.6 A Proposal for a Steganography GIS Model
In technical terms, public-key steganography is employed to realize a GIS that allows
authorized users to have access to secret information. The basic idea is that potential
users u i are associated with a couple of secret-key and public-key, < S K i , PK i >, that
are employed to exchange information with the other entities. The secret information
is embedded in the digital map with the public-key of the authorized users. Then, the
digital map may be delivered to all the users. However, the hidden content can be
extracted only by those users that own the corresponding secret-key that is used to
extract this information.
The main advantage of this approach is to convey different levels of strategic information in an innocuous way without raising suspicion in other potential users who
cannot be authorized to access some kind of information. In the scenario of a public
channel this solution is more appropriate than the use of cryptographic mechanisms
because encrypted content can easily be recognized. On the other hand, steganography content is indistinguishable from other content that does not contain hidden
information inside. In terms of security, one important requirement is the confidentiality of sensitive information.
Figure 11.5 shows the diagram of a GIS employing public-key steganography
to make sensitive content available only to authorized people. In the following, we
describe the functionality of this approach. As illustrated in Fig. 11.5(a), the sensitive
information (hidden content) is embedded in the digital map with the public-key PK i
of the potential users class u i . This produces a stego-map that can be visualized
differently according to the users that receive it. In fact, as illustrated in Fig. 11.5(b),
users visualize the stego-map by applying the extraction application. The extraction
application is composed of two extraction functions: Extract DM () and Extract HC ().
By applying the Extract DM () function, users retrieve the public digital map (cover).
By applying the Extract HC () function, users that own the corresponding secret-key
S K i are able to retrieve the hidden content, while users that do not own the right
secret-key are unable to notice any hidden content in the stego-map.
The embedding and extraction functions are illustrated in Table 11.2. A detailed
description of these functions is given in the following sections. Our aim is to provide
a GIS conceptual model that employs public-key steganography. We do not address
technical details about the implementation of this model, including, for example, the
number of GIS users or the possibility to employ multiple public-keys per user. Such
details strongly depend on the specific scenario; however, this issue goes outside the
scope of the chapter.