diff --git a/chapter-hsms/chapter.tex b/chapter-hsms/chapter.tex index 4813349..0313f77 100644 --- a/chapter-hsms/chapter.tex +++ b/chapter-hsms/chapter.tex @@ -112,9 +112,29 @@ cloning. This device will also be analyzed later in this chapter. \section{The Principles of Tamper-Sensing Mesh Construction and Monitoring} -\subsection{Security Mesh Manufacturing} +\subsection{Tamper-sensing Mesh Manufacturing} -\subsection{Security Mesh Monitoring} +The manufacturing technology of a tamper sensing mesh is a critical factor in its security. While in many applications, +meshes manufactured from off-the-shelf processes such as Flexible Printed Circuit (FPC) processes are used, these +processes tend to be optimzed to maximize the robustness of the produced circuits to mechanical stress. In contrast, the +ideal tamper-sensing mesh is exactly as robust as it needs to be not to be destroyed accidentially during normal +handling, but should not be more robust than that. As a result, more secure meshes tend to be manufactured in bespoke +manufacturing processes. +% FIXME cite Immler et al + +One more widely cited tamper-sensing mesh implementation is a commercial product developed by IBM in collaboration with +chemical company W.\ L.\ Gore \& Asscociates Inc.\ and used in IBM's datacenter HSM products up to approximately 2020. +% FIXME mention that Immler et al. cite them +This mesh design uses a stack of multiple layers of a clear, flexible plastic substrate on which carbon-based traces are +printed. Vias, i.e. contacts between layers, are made by laser cutting small holes into the substrate before the traces +are printed. The flexible circuit layers are joined with a opaque black, stretchy glue and after installation embedded +in an elastic opaque resin. The plastic substrate foil is thinner and significantly less resistant to tearing than +plastic substrates commonly used in the electronics industry for applications like key pads and circuit boards, which +improves its security against tampering. Furthermore, both the glue fusing the foil layers together and the resin the +mesh is embedded inside after installation are clearly co-designed with the carbon trace material such that the trace +material adheres well to both, leading to the traces being destroyed when either are peeled off. + +\subsection{Tamper-sensing Mesh Monitoring} \subsection{Other Tamper Sensing Techniques} @@ -122,7 +142,14 @@ cloning. This device will also be analyzed later in this chapter. \subsection{The Patent Landscape} -Tamper-sensing meshes can be implemented +Tamper-sensing meshes can be implemented in many different ways. Their design offers various degrees of freedom from the +precise conductor layout, through the manufacturing technology of the mesh and how it is wrapped around the payload +during manufacturing up to its monitoring circuitry. As a result, manufacturers across application domains from +datacenter appliance HSMs through card payment terminals and including niche applications like mail franking machines +have historically used patents on parts of their tamper-sensing mesh implementations as a means to prevent copying of +their designs. While most original tamper sensing mesh implementations are covered by at least one patent, we want to +highlight IBM for dwarfing the efforts of most other companies and fielding industry's widest portfolio of related +patents. \section{A Survey of Meshes in the Wild} @@ -208,7 +235,7 @@ cases. \subsubsection{Other miscellaneous devices} Sometimes, tamper-sensing meshes show up in other types of devices. We acquired two such devices. First, we acquired a -Neopost franking machine, a type of device that is used to directly print a code on an envelope that replaces a +Neopost mail franking machine, a type of device that is used to directly print a code on an envelope that replaces a conventional postage stamp. \section{Conclusion} diff --git a/chapter-introduction/chapter.tex b/chapter-introduction/chapter.tex index 3506dfc..7a96bde 100644 --- a/chapter-introduction/chapter.tex +++ b/chapter-introduction/chapter.tex @@ -190,7 +190,7 @@ In this thesis, we use the terms \emph{Tamper-Sensing Mesh} and \emph{Security M refer to any electrical circuit whose path is laid out to cover a surface with the intent of detecting attempts at drilling, cutting or otherwise manipulating this surface. While the term \emph{Security Mesh} is more concise, it is less clear to people unfamiliar with the matter. It is also polysemous, and depending on context can also refer to woven -or stamped metal meshes used as fences or as screens in front of windows to prevent break-in. As a result, it is harder +or stamped metal meshes used as fences or as screens in front of windows to prevent break-ins. As a result, it is harder to use in online searches, and when using Large Language Models (LLMs), it frequently leads to amusing hallucinations. %In the early days of mass-market computing, the expectations towards this new tool were high. Even before people