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Maria Calagna and Luigi V. Mancini
5.a)
STEGO−MAP
SENSITIVE MAP
PK_i
DIGITAL
MAP
HIDDEN
CONTENT
EMBED
5.b)
STEGO−MAP
HIDDEN
CONTENT
DIGITAL
MAP
EXTRACT
SK_i
SENSITIVE MAP
Fig. 11.5. GIS employs steganography to transmit sensitive information (hidden content) inside a digital map and makes this sensitive information available only to authorized people:
(a) illustrates how hidden content is embedded in a digital map in order to create a stego-map;
(b) illustrates how the users can extract the digital map, and eventually the hidden content,
from a stego-map
Table 11.2. The Embedding application is used to create a stego-map composed of a digital
map and possible sensitive content. The Extraction application retrieves all possible information from a stego-map, thus making the digital map, and eventually the hidden content,
accessible
Procedure Embedding
Procedure Extraction
Input:
DM, HC, PK i ;
Input:
S M, S K i ;
Embed(DM, HC) = S M;
Extract(S M) S K i = HC;
Output: S M
Output: DM, HC
11.6.1 The Embedding Application
The Embedding function takes a digital map DM, a content HC that represents the
secret to be hidden in the digital map ,and the public-key PK i of the class of users i
authorized to see the hidden content inside the digital map. The Embedding function
produces a stego-map S M as the final output. This map will be available to different
users, but it will be visualized differently by the recipients, as said before. The users