Improve survey chapter
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@ -324,46 +324,6 @@ Figure~\ref{fig_hsm_survey_sample_internal_pics}.
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\label{fig_hsm_survey_sample_pics}
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\end{figure}
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\begin{figure}
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\begin{tabular}[c]{cccc}
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\surveypic{01}{survey_internal_09_S01.jpg}&
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\surveypic{02}{survey_internal_20_S02.jpg}&
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\surveypic{03}{survey_internal_11_S03.jpg}&
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\surveypic{04}{survey_internal_03_S04.jpg}\\
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\surveypic{05}{survey_internal_10_S05.jpg}&
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\surveypic{06}{survey_internal_08_S06.jpg}&
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\surveypic{08}{survey_internal_24_S08.jpg}&
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\surveypic{09}{survey_internal_13_S09.jpg}\\
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\surveypic{10}{survey_internal_23_S10.jpg}&
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\surveypic{11}{survey_internal_17_S11.jpg}&
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\surveypic{12}{survey_internal_19_S12.jpg}&
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\surveypic{13}{survey_internal_02_S13.jpg}\\
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\surveypic{14}{survey_internal_00_S14.jpg}&
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\surveypic{14}{survey_internal_01_S14.jpg}&
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\surveypic{15}{survey_internal_04_S15.jpg}&
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\surveypic{16}{survey_internal_05_S16.jpg}\\
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\surveypic{17}{survey_internal_22_S17.jpg}&
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\surveypic{19}{survey_internal_26_S19.jpg}&
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\surveypic{20}{survey_internal_12_S20.jpg}\\
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\surveypic{21}{survey_internal_15_S21.jpg}&
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\surveypic{22}{survey_internal_16_S22.jpg}&
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\surveypic{23}{survey_internal_07_S23.jpg}&
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\surveypic{24}{survey_internal_06_S24.jpg}\\
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\surveypic{25}{survey_internal_25_S25.jpg}&
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\surveypic{27}{survey_internal_18_S27.jpg}&
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\surveypic{28}{survey_internal_14_S28.jpg}&
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\surveypic{30}{survey_internal_29_S30.jpg}\\
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\surveypic{31}{survey_internal_27_S31.jpg}&
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\surveypic{32}{survey_internal_28_S32.jpg}&
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% make sure the last row with a single dangling landscape picture is full height to avoid the last row's label
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% overlapping the previous row
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\rule{0pt}{25mm}
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\end{tabular}
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\caption{Internal overview photos of the survey samples}
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\label{fig_hsm_survey_sample_internal_pics}
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\end{figure}
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\subsubsection{Card Payment Terminals}
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Card payment terminals commonly include advanced tamper sensing features to discourage physical attacks such as
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@ -430,18 +390,72 @@ cases.
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Sometimes, tamper-sensing meshes show up in other types of devices. We acquired two such devices. First, we acquired a
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Neopost mail franking machine, a type of device that is used to directly print a code on an envelope that replaces a
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conventional postage stamp.
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conventional postage stamp. Since in businesses handling large volumes of mail these devices were routinely charged with large sums of
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money in postage, such devices have security features ranging from physical seals on their enclosure to full security
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meshes encasing their CPU modules. In case of Neopost, we are aware of one online source showing a security mesh inside
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one such device~\cite{mikeselectricstuffNeopostPostalFranking2023}, but we found that our older specimen only contained
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a sturdy cast zinc case that was welded shut with a spring-loaded lid switch inside. The other miscellaneous device we
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found is a broken CPU module from a German slot machine manufacturer. While it would be reasonable to assume this type
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of device might include active tamper sensing features to enforce state gambling regulations, other slot machine
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manufacturers seem not to use tamper sensing in their systems so the more likely reason is DRM. Our specimen included
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both a tamper-sensing mesh as well as a semiconductor junction light sensor inside of a sealed sheet metal enclosure.
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\subsection{Methodology}
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We proceeded by first photographing every test specimen from multiple angles, then disassembling them. After
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disassembly, we photographed each major component. After photos were taken, we proceeded with destructive techniques
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where necessary to obtain microscope photos of each tamper-sensing mesh component. PCBs were sectioned using a sanding
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drum attachment on a Dremel rotary tool. Potted modules were disassembled using milling, cutting and prying, applying
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heat from a heat gun as necessary to soften polymer compounds and to break glue joints.
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disassembly, we photographed each major component. Figure~\ref{fig_hsm_survey_sample_internal_pics} shows a selection of
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these photos showing the major internal components of the devices. After photos were taken, we proceeded with
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destructive techniques where necessary to obtain microscope photos of each tamper-sensing mesh component. PCBs were
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sectioned using a sanding drum attachment on a Dremel rotary tool. Potted modules were disassembled using milling,
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cutting and prying, and applying heat from a heat gun as necessary to soften polymer compounds and to break glue joints.
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\begin{figure}
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\begin{tabular}[c]{cccc}
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\surveypic{01}{survey_internal_09_S01.jpg}&
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\surveypic{02}{survey_internal_20_S02.jpg}&
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\surveypic{03}{survey_internal_11_S03.jpg}&
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\surveypic{04}{survey_internal_03_S04.jpg}\\
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\surveypic{05}{survey_internal_10_S05.jpg}&
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\surveypic{06}{survey_internal_08_S06.jpg}&
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\surveypic{08}{survey_internal_24_S08.jpg}&
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\surveypic{09}{survey_internal_13_S09.jpg}\\
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\surveypic{10}{survey_internal_23_S10.jpg}&
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\surveypic{11}{survey_internal_17_S11.jpg}&
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\surveypic{12}{survey_internal_19_S12.jpg}&
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\surveypic{13}{survey_internal_02_S13.jpg}\\
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\surveypic{14}{survey_internal_00_S14.jpg}&
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\surveypic{14}{survey_internal_01_S14.jpg}&
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\surveypic{15}{survey_internal_04_S15.jpg}&
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\surveypic{16}{survey_internal_05_S16.jpg}\\
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\surveypic{17}{survey_internal_22_S17.jpg}&
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\surveypic{18}{survey_internal_21_S18.jpg}&
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\surveypic{19}{survey_internal_26_S19.jpg}&
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\surveypic{20}{survey_internal_12_S20.jpg}\\
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\surveypic{21}{survey_internal_15_S21.jpg}&
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\surveypic{22}{survey_internal_16_S22.jpg}&
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\surveypic{23}{survey_internal_07_S23.jpg}&
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\surveypic{24}{survey_internal_06_S24.jpg}\\
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\surveypic{25}{survey_internal_25_S25.jpg}&
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\surveypic{27}{survey_internal_18_S27.jpg}&
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\surveypic{28}{survey_internal_14_S28.jpg}&
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\surveypic{30}{survey_internal_29_S30.jpg}\\
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\surveypic{31}{survey_internal_27_S31.jpg}&
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\surveypic{32}{survey_internal_28_S32.jpg}&
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% make sure the last row with a single dangling landscape picture is full height to avoid the last row's label
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% overlapping the previous row
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\rule{0pt}{25mm}
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\end{tabular}
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\caption{Internal overview photos of the survey samples}
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\label{fig_hsm_survey_sample_internal_pics}
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\end{figure}
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\subsection{Results}
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In the following sections, we will list some observations we made while dissecting our specimens. A complete set of
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internal pictures and micrographs of selected components that goes beyond the following description is available in the
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supplementary material to this thesis.
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\todo{Actually assemble the supplementary material and include all photos}
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\subsubsection{Mesh materials.}
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We found meshes constructed from rigid PCBs as well as a number of Flexible Printed Circuit (FPC) processes.
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Tamper-sensing meshes constructed from PCBs sometimes used parts of an existing PCB, and sometimes additional PCBs only
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