Secure Data Hiding in PDF Files Using
Encrypted Secret Message
Anahit Arshakyan
National Polytechnic University of Armenia
Overview
Used methods
 Data Hiding Using Encryption of the Secret Message
 Data Hiding Using the Compressed Stream
Generation method
Secret =
5%
Data Hiding Using Encryption of the Secret Message
PDF file stream
Secret
.txt
Clarification of the pdf file stream
Encoding
Representation of the secret message
symbols by the pdf stream encoding
Permutation Cypher
Data Hiding Using Encryption of the Secret Message
Cont
PDF file stream
Object containing Last stream
43
Secret Key:
•
•
•
•
•
Size of the Secret Data:
The number of symbols of the hidden data: 2
The number of symbols of positions used to store the hidden data: 287
Allocation of the hidden data within the cover-file structure: 3
Integral identifier used to determine the user preferences in data hiding: 1
Data Hiding Using Encryption of the Secret Message
Differences in Original and Derived XREF Tables
Original XREF
table
xref
0 9
0000000000
0000000015
0000000250
0000000320
0000000388
0000000564
0000000738
0000001413
0000001599
0000001812
65535
00000
00000
00000
00000
00000
00000
00000
00000
00000
Derived XREF
table
f
n
n
n
n
n
n
n
n
n
xref
0 9
0000000000
0000000015
0000000250
0000000363
0000000431
0000000607
0000000781
0000001464
0000001650
0000001863
65535
00000
00000
00000
00000
00000
00000
00000
00000
00000
f
n
n
n
n
n
n
n
n
n
Data Hiding Using Encryption of the Secret Message
Extracting
Start of the secret data: 287
Size of the secret data: 43
43
43 2 287 3 1
287
Secret .txt
Extracting
Data Hiding Using the Compressed Stream
 BT- points out to the beginning of the textual information
 ET-points out to the end of the textual information
 Tf – determines the font type and font size
 rg- determines the color
 Tj operator allocates the textual information, wrapped
into brackets, which is displayed on the screen when
reading
Data Hiding Using the Compressed Stream Cont
Secret.txt
Data Hiding Using the Compressed Stream
Extracting
Conclusion
The security of the proposed techniques are ensured through the secret
data cryptographic consealing in one, and decorating the secret under
the background segments of the cover files in the second, hiding
methods.
The stability of the proposed method is based on the complexity of
inverting hash tables and encryption scheme along with the data
unauthorized extraction intractability
Thank you
Three can keep a secret, if two of
them are dead
 The best place to hide is in plain sight…