Zero distortion-based steganography for handwritten signature
The growth of the Internet over the last few years has enabled many people and organisations, such as financial institutions, around the world communicate with each other and transfer information over public channels. In this light, public channels are used due the lack of private network infrast...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/71223/1/FK%202018%2078%20IR.pdf |
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| Summary: | The growth of the Internet over the last few years has enabled many people and
organisations, such as financial institutions, around the world communicate with each
other and transfer information over public channels. In this light, public channels are
used due the lack of private network infrastructure and high setup cost of private
networks. However, the data would be transferred through several different networks
before being delivered to the recipient and the information can be read or modified by
unauthorized user(s). To overcome this problem, steganography can be utilised as a
solution for privacy problems in public networks, such as the Internet, where many
digital media, such as images, audio and texts exist.
Moreover, with the advancement of steganography, several researchers have recently
devised steganalysis techniques, which threaten the steganographic systems. This
means that any changes on the cover media (c) could lead to the identification of the
stego media (s), which contains the secret message (m). Thus, developing a
steganographic algorithm to use cover media (c) without raising attention is the most
challenging task in data hiding. In this thesis, the human handwritten signature is
introduced as a novel cover media (c) in conjunction with a steganography algorithm
since there is a level of variability (i.e intra-user variability) within handwritten
signature samples of an individual. To the best of our knowledge, this is the first time
that a human handwritten signature sample is used for steganography application.
In its simplest form, the existence of intra-user variability within handwritten signature
samples of an individual is explored using the Kruskal-Wallis hypothesis test. Next,
hiding data was accomplished by implementing a signature synthesis technique to
produce a synthetic signature sample as a stego signature (s). This step was conducted by modelling both time series signals x and y (i.e. shape) of the handwritten signature
samples using the maximum overlap discrete wavelet transform (MODWT) and
several curve fitting techniques as the distortion function. Thus, the generated stego
signature (s) is used to make stego key (k) based on the zero-distortion approach to
represent the secret message (m) in a binary format. Finally, a computer numerical
control (CNC) machine is utilized to plot the stego signature (s) on a piece of A4 paper
for delivering to the recipient. On the other hand, by delivering the genuine signature
sample as well as the stego key (k) using different channels such as the Internet,
various image-processing techniques applied on the scanned stego signature (s) image
to reconstruct the secret message (m).
It was found that the acceptable range for the intra-user variability for genuine
signature samples in the SIGMA signature database can be shown as Mean ± 2STD
for both time series signals x and y. In addition, the imperceptibility rates of 3.5% and
4.7% were obtained for machine learning and human perception evaluation
approaches, respectively, when identifying the stego signatures (s). This study has
also demonstrated the payload capacity rate as 45.17%, which was the average
percentage of usage of the stego signature (s) for encoding the predefined secret
message (m). Finally, the proposed technique was able to retrieve the hidden data
using the selected offline stego signature sample (s), with 94.7% accuracy rate. |
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