From 599724f62c94b4a1c0de5f0f4f0da527e9a14d3b Mon Sep 17 00:00:00 2001 From: Paul Wortman Date: Mon, 27 Jul 2015 08:50:57 -0400 Subject: [PATCH] Edits, formatting, and additions to the PBD security paper - Formatting of first two sections - Formatting and combination of bullet points for PBD - Formatting, additions, and combinations of bullet points for Security section Signed-off-by: Paul Wortman --- PBDSecPaper.tex | 104 +++++++++++++++++++----------------------------- 1 file changed, 41 insertions(+), 63 deletions(-) diff --git a/PBDSecPaper.tex b/PBDSecPaper.tex index f38839d..e696f28 100644 --- a/PBDSecPaper.tex +++ b/PBDSecPaper.tex @@ -89,51 +89,30 @@ As systems move towards more complex designs and implementations (as allowed by \end{quotation} Work in the security realm is much more chaotic, although understakings have been made to define the scope of security and its intricacies in a well documented manner~\cite{Benzel2005}. Other work in the security realm includes security-aware mapping for automotive systems, explorations of dependable and secure computing, how to model secure systems, and defining the general theorems of security properties~\cite{Lin2013, Avizienis2004, Jorgen2008, Zakinthinos1997, Zhou2007}. Security has many facets to it: failure, processes, security mechanisms, secuirty principles, security policies, trust, etc. A key developing aspect of security is its standardization of encryption algorithms, methods of authentication, and communication protocol standards. \\ -Standardization is the process of developing and implementing technical standards. Standardization can help to maximinze compatability, interoperability, safety, repeatability, or quality; it can also faciliate commoditization of formerly custom processes. Standards appear in all sorts of domains. -\begin{itemize} -\item For the IC domain standardization manifests as a flexibile integrated circuit where customization for a particular application is achieved by programming one or more components on the chip (e.g. virtualization). PC makers and application software designers develop their products quickly and efficiently around a standard `platform' that emerged over time. As a quick over view of these standards: x86 ISA which makes is possible to reuse the OS \& SW applications, a full specified set of buses (ISA, USB, PCI) which allow for use of the same expansion boards of IC's for different products, and a full specification of a set of IO devices (e.g. keyboard, mouse, audio and video devices). The advantage of the standardization of the PC domain is that software can also be developed independently of the new hardware availability, thus offering a real hardware-software codesign approach. If the instruction set architecture (IAS) is kept constant (e.g. standardized) then software porting, along with future development, is far easier~\cite{Vincentelli2002}. In a `System Domain' lens, standardization is the aspect of the capabilities a platform offeres to develop quickly new applications (adoptability). In other words, this requires a distillation of the principles so that a rigorous methodology can developed and profitably used across different design domains. -\item So why is standardization useful? Standardization allows for manufacturers, system developers, and software designers to all work around a single, accepted, platform. It is understood what the capabilities of the hardware are, what the limitations of system IO will be, along with what the methods/protocols of communication will be. Even these preset aspects of the `standard' have their own `contractual obligations' of how they will function, what their respective `net-lists' are, and where the limtations of such standards lie. While the act of creating a standard takes time, not only due to time of development but due to speed of adoption of wide use, it is a necessary step. Without standarization, it becomes far more difficult to create universally used complex systems, let alone validate their correctness and trustworthiness. -\end{itemize} +Standardization is the process of developing and implementing technical standards. Standardization can help to maximinze compatability, interoperability, safety, repeatability, or quality; it can also faciliate commoditization of formerly custom processes. Standards appear in all sorts of domains. For the IC domain standardization manifests as a flexibile integrated circuit where customization for a particular application is achieved by programming one or more components on the chip (e.g. virtualization). PC makers and application software designers develop their products quickly and efficiently around a standard `platform' that emerged over time. As a quick over view of these standards: x86 ISA which makes is possible to reuse the OS \& SW applications, a full specified set of buses (ISA, USB, PCI) which allow for use of the same expansion boards of IC's for different products, and a full specification of a set of IO devices (e.g. keyboard, mouse, audio and video devices). The advantage of the standardization of the PC domain is that software can also be developed independently of the new hardware availability, thus offering a real hardware-software codesign approach. If the instruction set architecture (IAS) is kept constant (e.g. standardized) then software porting, along with future development, is far easier~\cite{Vincentelli2002}. In a `System Domain' lens, standardization is the aspect of the capabilities a platform offeres to develop quickly new applications (adoptability). In other words, this requires a distillation of the principles so that a rigorous methodology can developed and profitably used across different design domains. +So why is standardization useful? Standardization allows for manufacturers, system developers, and software designers to all work around a single, accepted, platform. It is understood what the capabilities of the hardware are, what the limitations of system IO will be, along with what the methods/protocols of communication will be. Even these preset aspects of the `standard' have their own `contractual obligations' of how they will function, what their respective `net-lists' are, and where the limtations of such standards lie. While the act of creating a standard takes time, not only due to time of development but due to speed of adoption of wide use, it is a necessary step. Without standarization, it becomes far more difficult to create universally used complex systems, let alone validate their correctness and trustworthiness. This is how one is able to change the current paradigm to a new standard model. -\begin{itemize} -\item Where do we gain/lose on shifting the method of design to a more platform-based design/security centric model? After all development of these tools implies that there is a need to change the focus and methods of design/development~\cite{Vincentelli2007}. - \begin{itemize} - \item The advatange to this method is ease of changes in development and searching of design spaces during early design and development of those systems. For PBD this means that a company/manufacturer is able to lower the cost and time spent in the `early development phase'; the time spent when first drawing up system designs prior to initial prototyping. While the advantage of overcoming multiple prototpying re-designs with a series of virtualization tools will cut down on development time, it can not be forgotten that rigorous standards and documentation need to be developed for this sort of advantage. Once this hurdle is passed then the advantages of such a system can be reaped. For security this means that components can be standardized from a local, network, and distributed standpoint. These different scopes of security will be tackled in Section~\ref{Security}. The main point here is that with standardization comes a form of `contract' that all parties can expect will be followed, thus allowing for a different manufacturers/developers to create different aspects of a system, while knowing that these different elements will come together in the final product; much like the advantages of platform-based design. - \item The disadvantage of using a new method is the loss in time for developing the standards, rigors, and documentation that would be used as new guide lines for the industry. These sorts of costs have been felt while developing any of the current standards of security; most definitely with the development of new algorithms for encryption. Further more, security vulnerabilities are found mainly due to incorrect implementations or due to incorrect assumptions about functionality; both of which are more easily avoidable with the use of rigorous planning and design. The other disadvantage is in the adoptability of these new methods. Ideally all manufacturers would adopt a new commodity; rather than components, `design combinations' would be the new commodity that manufacturers would peddle (e.g. instead of saying ``my components are the best'' the dialog moves towards ``My ability to combine these components is the best''). - \item Virtualization will help offset the time and monetary costs of using and implementing these new methodologies/ideologies. Essentially the issue boils down to how to abstract the lower level requirements of a system (assembly/C) into a simpler high level set of tools (API/block). A new set of tools needs to be developed that can be used to build bigger and greater things out of a series of smaller more manage/customizable blocks. Flexbilitiy of low level elements will help minimize conflict when attempting to design higher level blocks. As with any new system, there is a need for `tunable desings' that can be centered around specific aspects (e.g. power/energy efficient systems to minimize ``power cost buildup'', or security/trust centric needs). Functions, in this tool set, should be kept simple (e.g. decide output, \textbf{but} not how the output manifests). The reason behind this is that the design can remain simplistic in its [design and] operation. Virtualization tools lend to both the ideas of abstraction (choosing the simple output) and standardization/documentation (know what the outputs are, but not needing to know exactly how they manifest; just that they will)~\cite{Alagar2007}. They are a much needed tool for exploring design spaces and bringing codesign of software and hardware elements. - \end{itemize} -\item Hardware/Software Codesign - \begin{itemize} - \item There are different coding languages to handle different aspects (i.e. SW/HW) of vitrualization. When dealing with the virtualization of software the aspects of timing and concurrenccy semantics still fall short. These problems come from a lack of resolution and control at the lowest levels of virtualization interaction. The overwhelming hardware issue is that hardware semantics are very specific and tough to simulate. There has been the development of hardware simulation languages, such as SystemC~\cite{Kreku2008}, but there has not been the development of tools to bridge the space between hardware and software simulation/virtualization. Codesign of software simulations of hardware allows for development of high level software abstraction to interact with low level hardware abstraction. - \item The reasoning being the constant growth in complexity calls for simulation/virtualization of the design process. - \begin{itemize} - \item System-on-chip (SoC) technology will be already dominated by 100-1000 core multiprocessing on a chip by 2020~\cite{Teich2012}. Changes will affect the way companies design embedded software and new languages, and tool chains will need to emerge in order to cope with the enormous complexity. Low-cost embedded systems (daily-life devices) will undoubtably see development of concurrent software and exploitation of parallelism. In order to cope with the desire to include environment in the design of future cyber-physical systems, the heterogeneity will most definitely continue to grow as well in SoCs as in distributed systems of systems. - \item A huge part of design time is already spent on the verification, either in a simulative manner or using formal techniques~\cite{Teich2012}. ``Indeed, market data indicate that more than 80\% of system development efforts are now in software versus hardware. This implies that an effective platform has to offer a powerful design environment for software to cope with development cost.''~\cite{Vincentelli2002} Coverification will require an increasing proportion of the design time as systems become more complex. Progress at the electronic system level might diminish due to verification techniques that cannot cope with the modeling of errors and ways to retrieve and correct them, or, even better, prove that certian properties formulated as contraints during syntehsis will hold in the implementation by construction. The verification process on one level of abstraction needs to prove that an implementation (the structural view) indeed satisfies the specification (behavioral view)~\cite{Teich2012}. - \item The uncertainty of environment and communication partners of complex interacting cyber-physical systems, runtime adaptivity will be a must for guaranteeing the efficiency of a system. Due to the availability of reconfigurable hardware and multicore processing, which will also take a more important role in the tool chain for system simulation and evaluation, online codesign techniques will work towards a standard as time moves forward. - \end{itemize} - \item As with any design problem, if the functional aspects are indistinguishable from the implementation aspects, then it is very difficult to evolve the design over multiple hardware generations~\cite{Vincentelli2007}. It should be noted that there are tools that already exists for low, or high, system simulation. New terretory is the combination of these tools to form a `hardware-to-software' virtualization tool that is both efficient and effective. - \end{itemize} -\item Metropolis is one tool that is based in part on the concept of platform-based design. Metropolis can analyze statically and dynamically functional designs with models that have no notion of physical quantities and mapped designs where the association of functionality to architectural services allows for evaluation of characteristics (e.g.~latency, throughput, power, and energy) of an implementation of a particular functionality with a particular platform instance~\cite{Vincentelli2007, Metropolis}. Metropolis is but one manifestation of platform-based design as a tool. PBD has been used for the platform-exploration of synthetic biological systems as seen in the work done by Densmore et.~al.~to create a strong and flexable tool~\cite{Densmore2009}. Other applications, of platform-based design, include design on a JPEG encoder, imaging, and use for distributed automotive design~\cite{Vincentelli2007, Sedcole2006, }\textbf{ADD ALL CITING OF OTHER PBD BASED WORK HERE!!!}. -\end{itemize} +What is gained, and lost, when shifting the method of design to a more platform-based design/security centric model? After all development of these tools implies that there is a need to change the focus and methods of design/development~\cite{Vincentelli2007}. The advatange to this method is ease of changes in development and searching of design spaces during early design and development of those systems. For PBD this means that a company/manufacturer is able to lower the cost and time spent in the `early development phase'; the time spent when first drawing up system designs prior to initial prototyping. While the advantage of overcoming multiple prototpying re-designs with a series of virtualization tools will cut down on development time, it can not be forgotten that rigorous standards and documentation need to be developed for this sort of advantage. Once this hurdle is passed then the advantages of such a system can be reaped. For security this means that components can be standardized from a local, network, and distributed standpoint. These different scopes of security will be tackled in Section~\ref{Security}. The main point here is that with standardization comes a form of `contract' that all parties can expect will be followed, thus allowing for a different manufacturers/developers to create different aspects of a system, while knowing that these different elements will come together in the final product; much like the advantages of platform-based design. The disadvantage of using a new method is the loss in time for developing the standards, rigors, and documentation that would be used as new guide lines for the industry. These sorts of costs have been felt while developing any of the current standards of security; most definitely with the development of new algorithms for encryption. Further more, security vulnerabilities are found mainly due to incorrect implementations or due to incorrect assumptions about functionality; both of which are more easily avoidable with the use of rigorous planning and design. The other disadvantage is in the adoptability of these new methods. Ideally all manufacturers would adopt a new commodity; rather than components, `design combinations' would be the new commodity that manufacturers would peddle (e.g. instead of saying ``my components are the best'' the dialog moves towards ``My ability to combine these components is the best''). + +Virtualization will help offset the time and monetary costs of using and implementing these new methodologies/ideologies. Essentially the issue boils down to how to abstract the lower level requirements of a system (assembly/C) into a simpler high level set of tools (API/block). A new set of tools needs to be developed that can be used to build bigger and greater things out of a series of smaller more manage/customizable blocks. Flexbilitiy of low level elements will help minimize conflict when attempting to design higher level blocks. As with any new system, there is a need for `tunable desings' that can be centered around specific aspects (e.g. power/energy efficient systems to minimize ``power cost buildup'', or security/trust centric needs). Functions, in this tool set, should be kept simple (e.g. decide output, \textbf{but} not how the output manifests). The reason behind this is that the design can remain simplistic in its [design and] operation. Virtualization tools lend to both the ideas of abstraction (choosing the simple output) and standardization/documentation (know what the outputs are, but not needing to know exactly how they manifest; just that they will)~\cite{Alagar2007}. They are a much needed tool for exploring design spaces and bringing codesign of software and hardware elements. + +Hardware/Software codesign is crucial for bridging together the software and hardware aspects of a new system in an efficient and effective manner. There are different coding languages to handle different aspects (i.e. SW/HW) of vitrualization. When dealing with the virtualization of software the aspects of timing and concurrenccy semantics still fall short. These problems come from a lack of resolution and control at the lowest levels of virtualization interaction. The overwhelming hardware issue is that hardware semantics are very specific and tough to simulate. There has been the development of hardware simulation languages, such as SystemC~\cite{Kreku2008}, but there has not been the development of tools to bridge the space between hardware and software simulation/virtualization. Codesign of software simulations of hardware allows for development of high level software abstraction to interact with low level hardware abstraction. The reasoning being the constant growth in complexity calls for simulation/virtualization of the design process. System-on-chip (SoC) technology will be already dominated by 100-1000 core multiprocessing on a chip by 2020~\cite{Teich2012}. Changes will affect the way companies design embedded software and new languages, and tool chains will need to emerge in order to cope with the enormous complexity. Low-cost embedded systems (daily-life devices) will undoubtably see development of concurrent software and exploitation of parallelism. In order to cope with the desire to include environment in the design of future cyber-physical systems, a system's heterogeneity will most definitely continue to grow as well in SoCs as in distributed systems of systems. A huge part of design time is already spent on the verification, either in a simulative manner or using formal techniques~\cite{Teich2012}. ``Indeed, market data indicate that more than 80\% of system development efforts are now in software versus hardware. This implies that an effective platform has to offer a powerful design environment for software to cope with development cost.''~\cite{Vincentelli2002} Coverification will require an increasing proportion of the design time as systems become more complex. Progress at the electronic system level might diminish due to verification techniques that cannot cope with the modeling of errors and ways to retrieve and correct them, or, even better, prove that certian properties formulated as contraints during syntehsis will hold in the implementation by construction. The verification process on one level of abstraction needs to prove that an implementation (the structural view) indeed satisfies the specification (behavioral view)~\cite{Teich2012}. The uncertainty of environment and communication partners of complex interacting cyber-physical systems, runtime adaptivity will be a must for guaranteeing the efficiency of a system. Due to the availability of reconfigurable hardware and multicore processing, which will also take a more important role in the tool chain for system simulation and evaluation, online codesign techniques will work towards a standard as time moves forward. As with any design problem, if the functional aspects are indistinguishable from the implementation aspects, then it is very difficult to evolve the design over multiple hardware generations~\cite{Vincentelli2007}. It should be noted that there are tools that already exists for low, or high, system simulation. New territory is the combination of these tools to form a `hardware-to-software' virtualization tool that is both efficient and effective. +Metropolis is one tool that is based in part on the concept of platform-based design. Metropolis can analyze statically and dynamically functional designs with models that have no notion of physical quantities and mapped designs where the association of functionality to architectural services allows for evaluation of characteristics (e.g.~latency, throughput, power, and energy) of an implementation of a particular functionality with a particular platform instance~\cite{Vincentelli2007, Metropolis}. Metropolis is but one manifestation of platform-based design as a tool. PBD has been used for the platform-exploration of synthetic biological systems as seen in the work done by Densmore et.~al.~to create a strong and flexable tool~\cite{Densmore2009}. Other applications, of platform-based design, include design on a JPEG encoder, imaging, and use for distributed automotive design~\cite{Vincentelli2007, Sedcole2006, }\textbf{ADD ALL CITING OF OTHER PBD BASED WORK HERE!!!}. \begin{itemize} -\item The manufacturer's standpoint boils down to: the design should minimize mask-making costs but be flexible enough to warrant its use for a set of applications so that production volume will be high over an extended chip lifetime~\cite{Vincentelli2007}. Companies try to drive adoptability by means of creating something that users want to interact with, but not be complicated to learn (e.g. abstraction of technology for ease of use). Accounting for ease of use can lead to vulnerabilities in security or the development of new tools. Automation is desirable from a `business' standpoint since customers/users enjoy the `set it and forget it' mentality for technology (especially new technologies). Companies/Manufacturers need positive customer/user experiences, otherwise there is no desire to extend any supplied functionality to any other devices/needs on the part of the consumer. Adoptablility tends to come from user `word of mouth' praising the functionality and ease of use of new technology/methods/devices and how the developing party reacts to system failures or user-need (branching from complaints and support requests). - \begin{itemize} - \item This is exactly why industry would love for platform-based design to become a new standard. The monetary costs saved would be enough to warrent adoption of the technology, \textbf{but} the monetary costs of developing such a system (e.g. design, evalutation, validation) does not carry the same attraction (simply because companies are selfish and want to \textbf{make} money). - \end{itemize} +\item The manufacturer's standpoint boils down to: the design should minimize mask-making costs but be flexible enough to warrant its use for a set of applications so that production volume will be high over an extended chip lifetime~\cite{Vincentelli2007}. Companies try to drive adoptability by means of creating something that users want to interact with, but not be complicated to learn (e.g. abstraction of technology for ease of use). Accounting for ease of use can lead to vulnerabilities in security or the development of new tools. Automation is desirable from a `business' standpoint since customers/users enjoy the `set it and forget it' mentality for technology (especially new technologies). Companies/Manufacturers need positive customer/user experiences, otherwise there is no desire to extend any supplied functionality to any other devices/needs on the part of the consumer. Adoptablility tends to come from user `word of mouth' praising the functionality and ease of use of new technology/methods/devices and how the developing party reacts to system failures or user-need (branching from complaints and support requests). This is exactly why industry would love for platform-based design to become a new standard; gain high adoptability. The monetary costs saved would be enough to warrent adoption of the technology, \textbf{but} the monetary costs of developing such a system (e.g. design, evalutation, validation) does not carry the same attraction (simply because companies are selfish and want to \textbf{make} money). \item Security concerns center around how to define trust/trustworthiness, determining the functions and behvaiors of security components, and the prinicples, policies, and mechanisms that are rigorously documented to standardize behavior. Also designed by industry to clearer standards, giving better security and ease of set-up and implementation. \end{itemize} \section{Platford-based design} \label{Platform-based design} -\begin{itemize} -\item The monetary considerations of platform-based design include system re-use, flexibility of elements, and re-programmability. As system complexity grows the costs of producing chips becomes more expensive, thus pushing for the systems that are produced to be ``multi-capable'' (e.g. re-use value)~\cite{Keutzer2000}. The greatest challenge in the hardware design space is placement and arragement of components based on an array of differing variables. Design of architecture platforms is a result of trade-off in complex space, and worse yet some aspects directly compete/contradict each other~\cite{Vincentelli2002, Gruttner2013}. - \begin{itemize} - \item The size of the application space that can be supported by the architectures belonging to the architecture platform represents the flexability of the platform. The size of the architecture space that satisfies the constraints embodied in the design architecture is what providers/manufacturers have in designing their hardware instances. Even at this level of abstraction these two aspects of hardware design can compete with each other. Ex: A manufacturer has pre-determined sizes that constrain their development space apriori. Further more, aspects such as design space constraints and heat distribution are a well known source of trouble when designing embedded systems. - \end{itemize} -\item As with any new technology/design methodoloy/concept there are expensive initial costs for development, evaluation, and validation until more rigorous documentation can be made. As with any early development, it pays to think everything through first before diving into prototyping (want roughly 90/10 split between planning and action; same as with software development). This can be aided through the development of virtualization tools; which unfortunately come with their own development, evaluation, and validation costs. Harping on this, two main concerns for effective platform-based design developement and adoptation are software developement and a set of tools that insulate the details of architecture from application software (e.g. virtualization). The more abstract the programmer's model, the richer is the set of platform instances, but the more difficult is to choose the ``optimal'' architecture platform instance and map automatically into it~\cite{Vincentelli2002}. -\item In PBD, the partitioning of the design into hardware and software is not the essence of system design as many think, rather it is a consequence of decisions taken at a higher level of abstraction~\cite{Vincentelli2007}. For example, a lower level consideration may be heat dissipation concerns which manifests itself as size constraints at higher levels. The types of decisions that are made at these higher levels lend to the design traits that are requirements at lower levels. These sort of complexities in cost of design are exactly why abstraction/virtualization are required/desired. Additional levels of abstraction (along with virtualization tools for design space exploration) aid in simplifying the design process. The abstraction levels deal with critical decisions that are about the architecture of the system, e.g., processors, buses, hardware accelerators, and memories, that will carry on the computation and communication tasks associated with the overall specification of the design~\cite{Vincentelli2007, Pellizzoni2009}. These critical paths are determined based on `pivot-points' or characteristics that restrict the behavior and function of a given elements/component, or can be based on requirements for function/behavior that are requested for by the end-user. In certain scenarios these critical decisions can be centered around `safety-critical' elements, as can be seen in embedded systems deployed in the medical market (e.g. pacemakers); these `safety-critical' elements being responsible for the wellness and health of its user. The library of functional and communication components is the design space that we are allowed to explore at the appropriate level of abstraction~\cite{Vincentelli2007}. There are elements of recursive behavior that need to be tackled from a virtualized tool standpoint. In a PBD refinement-based design process, platforms should be defined to eliminate large loop iterations for affordable designs~\cite{Vincentelli2007}. This refinement should restrict the design space via new forms of regularity and structure that surrender some design potential for lower cost and first-pass sucess. -\end{itemize} +Platform-based design is a methodology where function spaces are mapped to platform spaces (e.g. architectural space) or vica-versa. Generally the mapping of a function instance towards a platform instance leads to a larger subset of platform instances branching from a single function instance; as can be seen in Figure~\ref{fig:RecursivePBD}. Of course this relationship works in the reverse manner as well; a single platform instance maps to a subset of function instances. Although one can think of the mapping process as happening in one direction, or the other, platform-based design is a ``meet-in-the-middle'' approach. A designer/developer works towards merging two platforms (e.g. software functionality and hardware architectures) where the resulting `middle-ground', or mapping, can be thought of as its own `mapping instance'; merging an abstract higher level function with an abstraction lower level platform. More on the recusive nature of PBD will be explored later in this section, for now we will examine the benefits of using such a methodology. + +The monetary considerations of platform-based design include system re-use, flexibility of elements, and re-programmability. As system complexity grows the costs of producing chips becomes more expensive, thus pushing for the systems that are produced to be ``multi-capable'' (e.g. re-use value)~\cite{Keutzer2000}. The greatest challenge in the hardware design space is placement and arragement of components based on an array of differing variables. Design of architecture platforms is a result of trade-off in complex space, and worse yet some aspects directly compete/contradict each other~\cite{Vincentelli2002, Gruttner2013}. The size of the application space that can be supported by the architectures belonging to the architecture platform represents the flexability of the platform. The size of the architecture space that satisfies the constraints embodied in the design architecture is what providers/manufacturers have in designing their hardware instances. Even at this level of abstraction these two aspects of hardware design can compete with each other. Ex: A manufacturer has pre-determined sizes that constrain their development space apriori. Further more, aspects such as design space constraints and heat distribution are a well known source of trouble when designing embedded systems. + +As with any new technology/design methodoloy/concept there are expensive initial costs for development, evaluation, and validation until more rigorous documentation can be made. As with any early development, it pays to think everything through first before diving into prototyping (want roughly 90/10 split between planning and action; same as with software development). This can be aided through the development of virtualization tools; which unfortunately come with their own development, evaluation, and validation costs. Harping on this, two main concerns for effective platform-based design developement and adoptation are software developement and a set of tools that insulate the details of architecture from application software (e.g. virtualization). The more abstract the programmer's model, the richer is the set of platform instances, but the more difficult is to choose the ``optimal'' architecture platform instance and map automatically into it~\cite{Vincentelli2002}. + +In PBD, the partitioning of the design into hardware and software is not the essence of system design as many think, rather it is a consequence of decisions taken at a higher level of abstraction~\cite{Vincentelli2007}. For example, a lower level consideration may be heat dissipation concerns which manifests itself as size constraints at higher levels. The types of decisions that are made at these higher levels lend to the design traits that are requirements at lower levels. These sort of complexities in cost of design are exactly why abstraction/virtualization are required/desired. Additional levels of abstraction (along with virtualization tools for design space exploration) aid in simplifying the design process. The abstraction levels deal with critical decisions that are about the architecture of the system, e.g., processors, buses, hardware accelerators, and memories, that will carry on the computation and communication tasks associated with the overall specification of the design~\cite{Vincentelli2007, Pellizzoni2009}. These critical paths are determined based on `pivot-points' or characteristics that restrict the behavior and function of a given elements/component, or can be based on requirements for function/behavior that are requested for by the end-user. In certain scenarios these critical decisions can be centered around `safety-critical' elements, as can be seen in embedded systems deployed in the medical market (e.g. pacemakers); these `safety-critical' elements being responsible for the wellness and health of its user. The library of functional and communication components is the design space that we are allowed to explore at the appropriate level of abstraction~\cite{Vincentelli2007}. There are elements of recursive behavior that need to be tackled from a virtualized tool standpoint. In a PBD refinement-based design process, platforms should be defined to eliminate large loop iterations for affordable designs~\cite{Vincentelli2007}. This refinement should restrict the design space via new forms of regularity and structure that surrender some design potential for lower cost and first-pass sucess. \begin{figure*} \includegraphics[width=\textwidth,height=8cm]{./images/recursivePBD.png} @@ -141,34 +120,28 @@ Standardization is the process of developing and implementing technical standard \label{fig:RecursivePBD} \end{figure*} -\begin{itemize} -\item Due to the recursive nature of platform-based design, establishing the number, location, and components of intermediate ``platforms'' is the essence of PBD~\cite{Vincentelli2007}. In fact, designs with different requirements and specifications may use different intermediate platforms, hence different layers of regularity and design-space constraints per scenarios. The tradeoffs involved in the selection of the number and characteristics of platforms relates to the size of the design space to be explored and the accuracy of the estimation of the chracteristics of the solution adopted. Naturally, the larger the step across platforms, the more difficult is predicting performance, optimizing at the higher levels of abstraction, and providing a tight lower bound. In fact, the design space for this approach may actually be smaller than the one obtained with smaller steps because it becomes harder to explore meaningful design alternatives and the restriction on the search space impedes complete design-space exploration. Ultimately, predictions/abstractions may be so inaccurate that design optimizations are misguided and the lower bounds are incorrect~\cite{Vincentelli2007}. On the other hand, having minimally small steps across the design space leads to needless complexity and unnecessary refinement of abstraction levels. The identification of precisely defined layers where the mapping processes takes place is an important design decision and should be agreed upon at the top design management level or during the initial early design phase of the system~\cite{Vincentelli2007}. As can be seen in Figure~\ref{fig:RecursivePBD}, each layer supports a design stage where the performance indexes that characterize the architectural components provide an opaque abstraction of lower layers that allows accurate performance estimations to be used to guide the mapping process~\cite{Vincentelli2007}. Standardization, or atleast some abstraction rule documentation, is what will greatly lend to minimizing the costs of using platform-based design. It is here that one clearly sees the recursive nature of this design methodology, and hopefully, also is able to see the advantages of the wide adoptation of platform-based design. -\item This approach results in better reuse, because it decouples independent aspects, that would otherwise be tired, e.g., a given functional specification to low-level implementation details, or to a specific communication paradigm, or to a scheduling algorithm~\cite{Vincentelli2007}. Coupled with well developed software virtualization tools, this would allow for better exploration of initial design spaces but does come at a cost of a rigorous, documented, standardization. +Due to the recursive nature of platform-based design, establishing the number, location, and components of intermediate ``platforms'' is the essence of PBD~\cite{Vincentelli2007}. In fact, designs with different requirements and specifications may use different intermediate platforms, hence different layers of regularity and design-space constraints per scenarios. The tradeoffs involved in the selection of the number and characteristics of platforms relates to the size of the design space to be explored and the accuracy of the estimation of the chracteristics of the solution adopted. Naturally, the larger the step across platforms, the more difficult is predicting performance, optimizing at the higher levels of abstraction, and providing a tight lower bound. In fact, the design space for this approach may actually be smaller than the one obtained with smaller steps because it becomes harder to explore meaningful design alternatives and the restriction on the search space impedes complete design-space exploration. Ultimately, predictions/abstractions may be so inaccurate that design optimizations are misguided and the lower bounds are incorrect~\cite{Vincentelli2007}. On the other hand, having minimally small steps across the design space leads to needless complexity and unnecessary refinement of abstraction levels. The identification of precisely defined layers where the mapping processes takes place is an important design decision and should be agreed upon at the top design management level or during the initial early design phase of the system~\cite{Vincentelli2007}. As can be seen in Figure~\ref{fig:RecursivePBD}, each layer supports a design stage where the performance indexes that characterize the architectural components provide an opaque abstraction of lower layers that allows accurate performance estimations to be used to guide the mapping process~\cite{Vincentelli2007}. Standardization, or atleast some abstraction rule documentation, is what will greatly lend to minimizing the costs of using platform-based design. It is here that one clearly sees the recursive nature of this design methodology, and hopefully, also is able to see the advantages of the wide adoptation of platform-based design. This approach results in better reuse, because it decouples independent aspects, that would otherwise be tired, e.g., a given functional specification to low-level implementation details, or to a specific communication paradigm, or to a scheduling algorithm~\cite{Vincentelli2007}. Coupled with well developed software virtualization tools, this would allow for better exploration of initial design spaces but does come at a cost of a rigorous, documented, standardization. \begin{quotation} ``It is very important to define only as many aspects as needed at every level of abstraction, in the interest of flexibility and rapid design-space exploration.''~\cite{Vincentelli2007} \end{quotation} The issue of platform-based design is not so much an over-engineering of design/development, but rather a need to strike a balance between all aspects of design; much like what already happens in hardware and software design. -\end{itemize} \section{Security} \label{Security} -\begin{itemize} -\item Evolving with time and understanding as knowledge of encryption and other security encapsulation techniques. There are considerations that are accounted from a software standpoint: capabilities of the software, speed of the algorthims/actions that take place, and how unique (level of uniqueness) a given solution is. Similarly there are hardware considerations as well: tolerance of the chip elements in use, their capabilities, power distribution over the entire hardware design, signal lag between different elements, and cross-talk caused by communication channels. Different groups have tackled aspects of these considerations. -\item The Trusted Computing Group (TCG) created Trusted Platform Modules (TPM) which are able to validate their own functionality and if the TPMs have been tampered with. This is, in essence, a method of `self-analysis'; thus the ground work for a `self-analyzing' security component is already in place. This self checking can be used as a method for allowing the larger system of security components to locate damaged/error-prone componenets so that they can be replaced/fixed thus raising the overall trustworthiness of the system of components. Therefore TPMs are a good stepping stone on the path for better security, but TPM/TCG has no found ``the answer'' yet~\cite{Sadeghi2008}. -\item Another example of security/trustworthiness implementation is the use of monitors for distributed system security. Different methods are used for determining trust of actions (e.g. Byzantine General Problem). These methods are used for determining the most sane/trustworhy machine out of a distributed network so that users know they are interacting with the `freshest' data at hand. While the realm of distributed systems has found good methods/principles to govern their actions/updates of systems. These methods are by no means `final' or perfect but will rather develop with time. As one can see, there are solutions implemented across a series of different HW and SW platforms for tackling different aspects of security. The unifying factor in all of them is determining what is or isn't trustworthy. -\item The definition of ``trustworthiness'' that is chosen to help color this perspective on security is as defined in the Benzel et.~al.~paper. +Security is always evolving with time and understanding as knowledge of encryption and other security encapsulation techniques change over time. There are considerations that are accounted from a software standpoint: capabilities of the software, speed of the algorthims/actions that take place, and how unique (level of uniqueness) a given solution is. Similarly there are hardware considerations as well: tolerance of the chip elements in use, their capabilities, power distribution over the entire hardware design, signal lag between different elements, and cross-talk caused by communication channels. Different groups have tackled aspects of these considerations. The Trusted Computing Group (TCG) created Trusted Platform Modules (TPM) which are able to validate their own functionality and if the TPMs have been tampered with. This is, in essence, a method of `self-analysis'; thus the ground work for a `self-analyzing' security component is already in place. This self checking can be used as a method for allowing the larger system of security components to locate damaged/error-prone componenets so that they can be replaced/fixed thus raising the overall trustworthiness of the system of components. Therefore TPMs are a good stepping stone on the path for better security, but TPM/TCG has no found ``the answer'' yet~\cite{Sadeghi2008}. Another example of security/trustworthiness implementation is the use of monitors for distributed system security. Different methods are used for determining trust of actions (e.g. Byzantine General Problem). These methods are used for determining the most sane/trustworhy machine out of a distributed network so that users know they are interacting with the `freshest' data at hand. While the realm of distributed systems has found good methods/principles to govern their actions/updates of systems. These methods are by no means `final' or perfect but will rather develop with time. As one can see, there are solutions implemented across a series of different HW and SW platforms for tackling different aspects of security. The unifying factor in all of them is determining what is or isn't trustworthy. + +The definition of ``trustworthiness'' that is chosen to help color this perspective on security is as defined in the Benzel et.~al.~paper. \begin{quotation} ``\textit{Trustworthy} (noun): the degree to which the security behavior of the component is demonstrably compliant with its stated functionality (\textit{e.g., trustworthy component}). \\ \textit{Trust}: (verb) the degree to which the user or a component depends on the trustworthiness of another component. For example, component A \textit{trusts} component B, or component B is \textit{trusted} by component A. Trust and trustworthiness are assumed to be measured on the same scale.''~\cite{Benzel2005} \end{quotation} - \begin{itemize} - \item Dependability is a measure of a system's availability, reliability, and its maintainability. Furthermore, Avizienis et.~al.~extends this to also encompass mechanisms designs to increase and maintain the dependability of a system~\cite{Avizienis2004}. For the purpose of this paper, the interpretation is that trustworthiness requires inherrent dependability; i.e. a user should be able to trust that trustworthy components will dependably perform the desired actions and alert said user should an error/failure occur. - \item Unfortunately the measurement of trust(worthiness) is measured using the same, abstract scale~\cite{Benzel2005}. Thus, in turn, there is a void for the design and development of an understandable and standardized scale of trust(worthiness). Which could then lead to a change of paradigm in the methods by which security policies, mechanisms, and principles are implemented and evolve. - \item ``In order to develop a component-based trustworthy system, the development process must be reuse-oriented, component-oriented, and must integrate formal languages and rigorous methods in all phases of system life-cycle.''~\cite{Mohammed2009} Component-Based Software Engineering (CBSE) is widely adopted in the software industry as the mainstream approach to software engineering~\cite{Mohammed2009, Mohammad2013}. CBSE is a reuse-based approach of defining, implementing and composing loosely coupled independent components into systems and emphasizes the separation of concerns in respect of the wide-ranging functionality available throughout a given software system. Thus it can be seen that the ideals being outlined in this paper are already in use, all that is needed is their re-application to a new design methodology. In a way one can see CBSE as a restricted-platform version of platform-based design. This furthers this paper's point, that the required elements for combining PBD and security are already in use for different purposes and simply need to be `re-purposed' for this new security centric platform-based design. - \begin{quotation} - ``Most prevalent trust models only focus on assessing trustworthiness of systems at runtime, and do not provide necessary predictions of the trust of systems before they are built. This makes improving trustworthiness of the composed system to be costly and time-consuming. Therefore it is important to consider trust of the composed software system at the development time itself.''~\cite{Gamage} - \end{quotation} - \end{itemize} -\end{itemize} +Dependability is a measure of a system's availability, reliability, and its maintainability. Furthermore, Avizienis et.~al.~extends this to also encompass mechanisms designs to increase and maintain the dependability of a system~\cite{Avizienis2004}. For the purpose of this paper, the interpretation is that trustworthiness requires inherrent dependability; i.e. a user should be able to trust that trustworthy components will dependably perform the desired actions and alert said user should an error/failure occur. Unfortunately the measurement of trust(worthiness) is measured using the same, abstract scale~\cite{Benzel2005}. Thus, in turn, there is a void for the design and development of an understandable and standardized scale of trust(worthiness). Which could then lead to a change of paradigm in the methods by which security policies, mechanisms, and principles are implemented and evolve. +\begin{quotation} +``In order to develop a component-based trustworthy system, the development process must be reuse-oriented, component-oriented, and must integrate formal languages and rigorous methods in all phases of system life-cycle.''~\cite{Mohammed2009} +\end{quotation} +Component-Based Software Engineering (CBSE) is widely adopted in the software industry as the mainstream approach to software engineering~\cite{Mohammed2009, Mohammad2013}. CBSE is a reuse-based approach of defining, implementing and composing loosely coupled independent components into systems and emphasizes the separation of concerns in respect of the wide-ranging functionality available throughout a given software system. Thus it can be seen that the ideals being outlined in this paper are already in use, all that is needed is their re-application to a new design methodology. In a way one can see CBSE as a restricted-platform version of platform-based design. This furthers this paper's point, that the required elements for combining PBD and security are already in use for different purposes and simply need to be `re-purposed' for this new security centric platform-based design. +\begin{quotation} +``Most prevalent trust models only focus on assessing trustworthiness of systems at runtime, and do not provide necessary predictions of the trust of systems before they are built. This makes improving trustworthiness of the composed system to be costly and time-consuming. Therefore it is important to consider trust of the composed software system at the development time itself.''~\cite{Gamage} +\end{quotation} \begin{figure*} \includegraphics[width=\textwidth,height=10cm]{./images/SecurityDesignMap.png} @@ -181,10 +154,7 @@ The issue of platform-based design is not so much an over-engineering of design/ \begin{itemize} \item Local (self) \begin{itemize} - \item The local scope encompasses a security element's own abilities, trustworthiness, and the dependencies of that element (e.g. least common mechanisms, reduced complexity, minimized sharing, and the conflict between this as least common mechanisms). The purpose of this section is to present the considerations, principles, and policies that govern the behavior and function of security elements/components at the local scope/level. - \item Failure - a condition in which, given a specifically documented input that conforms to specification, a component or system exhibits behavior that deviates from its specified behavior. - \item Module/Database - a unit of computation that encapsulates a database and provides an interface for the initialization, modification, and retireval of information from the database. The database may be either implicit, e.g. an algorithm, or explicit. - \item Process(es) - a program(s) in execution. + \item The local scope encompasses a security element's own abilities, trustworthiness, and the dependencies of that element (e.g. least common mechanisms, reduced complexity, minimized sharing, and the conflict between this as least common mechanisms). The purpose of this section is to present the considerations, principles, and policies that govern the behavior and function of security elements/components at the local scope/level. First, this paper will reiterate the definitions stated in the Benzel et.~al.~paper. Failure is a condition in which, given a specifically documented input that conforms to specification, a component or system exhibits behavior that deviates from its specified behavior. A module/database is seen as a unit of computation that encapsulates a database and provides an interface for the initialization, modification, and retireval of information from the database. The database may be either implicit, e.g. an algorithm, or explicit. Lastly, a process(es) is a program(s) in execution. To further define the actions/behavior of a given component in the local scope, this paper moves to outlinging the principles that define component behavior at the local device level. \item Least Common Mechanisms - If multiple components in the system require the same function of mechanism, then there should be a common mechanism that can be used by all of them; thus various components do not have separate implementations of the same function but rather the function is created once (e.g. device drivers, libraries, OS resource managers). The benefit of this being to minimize complexity of the system by avoiding unnecessary duplicate mechanims. Furthermore, modifications to a common function can be performed (only) once and impact of the proposed modifications allows for these alterations to be more easily understood in advance. \item Reduced Complexity - The simpler a system is, the fewer vulnerabilities it will have. From a security perspective, the benefit to this simplicity is that is is easier to understand whether an intended security policy has been captured in system design. At a security model level, it can be easier to determine whether the initial system state is secure and whether subsequent state changes preserve the system security. Given current state of the art of systems, the conservative assumption is that every complex system will contain vulnerabilities and it will be impossible to eliminate all of them, even in the most highly trustworthy of systems. \item Minimized Sharing - At the lowest level of secure data, no computer resource should be shared between components or subjects (e.g. processes, functions, etc.) unless it is necessary to do so. To protect user-domain information from active entities, no information should be shared unless that sharing has been explicitly requested and granted. Encapsulation is a design discipline or compiler feature for ensuring there are no extraneous execution paths for accessing private subsets of memory/data. Minimized sharing influenced by common mechanisms can lead to designs being reentrant/virtualized so that each component depending mechanism will have its own virtual private data space; parition resources into discrete, private subsets for each dependent component. This in turn can be seen as a virtualization of hardware, a concept already illustrated earlier with the discussion of platform-based design. A further consideration of minimized sharing is to avoid covert timing channels in which the processor is one of the shared components. In other words, the scheduling algorithms must ensure that each depending component is allocated a fixed amount of time to access/interact with a given shared space/memory. Development of a technique for controlled sharing requires execution durations of shared mechanisms (or mechanisms and data structures that determine duration) to be explicitly stated in design specification documentation so that effects of sharing can be verified and evaluated. Once again illustrating the need for rigorous standards to be clearly documented. @@ -238,7 +208,7 @@ The issue of platform-based design is not so much an over-engineering of design/ \item In the same manner that these various security aspects (e.g. mechanisms, principles, policies) must be considered during development automation, the software and hardware aspects must also come under consideration based on the desired behavior/functionality of the system under design. One could have security elements that attempt to optimize themselves to the system they are in based on a few pivot points (power, time, efficiency, level of randomness). Another option for the automated tool could trade out specific security components as an easier way to increase security without requiring re-design/re-construction of the underlying element (e.g. modularity). There is always the requirement that the overall trustworthiness of a new system must meet the standards of the security policies that `rule' the system. For these reasons a user would desire rigorous documentation that would lay out the requirements of each component, so that in the case of trying to replace faulty or damaged components there would be no loss to the overall trustworthiness of the system; while also not introducing any vulnerabilities due to the inclusion of new system components. \item Virtualization should be used for exploring the design space; it is hoped that it is obvious as to why. Not only is the cost of prototyping incredably expensive, but redesign is equally costly. Virtualization aids by removing the need for physical prototyping (less monitary costs) and allows for more rapid exploration of the full design space. While the design time for such powerful tools will be expensive (both in monitary and temporal costs), the rewards of developing, validating, and evaluating this virtualization tool will offset the early design phase costs of automated security component design. \end{itemize} -\item Mapping of Security onto PBD structure +\item Mapping of Security onto PBD structure. At this point, it is the hope of the author that the reader can see how the needs and benefits of platform-based design and security development are closely aligned along the same concepts of rigorous design, virtualization/automation of tools, and the needs for meticulous documentation. The reasoning for using platform-based design is that PBD functions as a form of `architecural base' upon which security development can be mapped over. PBD can be used for development of hardware elements, security centric SoCs, or even as a set of abstract blocks that can be used to design higher level applications (e.g. virtualization development of larger security systems). But as with the development of any tool, and more so when expecting said tools to be more publically used, there is a deep need for meticulous documentation and rigorous use/distribution of standards. without this, there is no guarentee that anyone will benefits from use of this new model. Much like with security inovation and implementation, without proper outlining of behavior and function there is greater possiblity for erroneous use thus leading to greater vulnerability of the overall system. \begin{itemize} \item ``Despite occasional cryptology-related attacks, most security vulnerabilities result from poor software design and implementation, such as the ever-lasting buffer overrun bugs. Thus approaches to designing secure software, not just from a traditional cryptology viewpoint, but with a software engineering perspective, are needed to counter the current unsatisfactory situation.''~\cite{Ren2006} \item Focusing efforts on rigorous design documentation allows security concerns to be recognized early in the development process and these aspects can be given sufficient attention in subsequent stages of the device's life cycle. ``By controlling system security during architectural refinement, we can decrease software production costs and speed up the time to market~\cite{ZhouFoss2006}.'' This approach also enchances the role of the software architects by requiring that their decisions be not only for functional decomposition, but also for non-functional requirements fulfillment. Hence, virtualization/automation of security development is not only effective but also enticing. @@ -259,10 +229,12 @@ The issue of platform-based design is not so much an over-engineering of design/ \end{itemize} \item \textbf{DRAW CONNECTIONS TO SECURITY DEVELOPMENT AND PBD TO SHOW HOW THESE TWO CAN BE MAPPED TOGETHER. BE SURE TO STATE THE OBVIOUS!!! MAKE THE POINT OF THIS PAPER!} \end{itemize} -\item The last, and by no means least, important topic that must be tackled in this section is the question of what exactly are the research challenges. There has been a lot of information, ideas, and principles presented over the course of this writing along with parallels to existing research and methodologies that can be almost directly applied to the concept of mapping security development to platform-based design. The primary cost of developing security, and running a secure system, is time. There are the monitary and hardware costs of security developement and implementation, but even those aspects all have a time cost coupled with them. Time, while being the most expensive part of security design is also the aspect that can be tackled and minimized with rigorous planning and documentation. Taking into account that even the development of documentation and standards also has its own time cost associated with it, this early phase development can also diminsh the time-cost impact for later steps in the system's development/implementation life-cycle. +\item The last, and by no means least, important topic that must be tackled in this section is the question of what exactly are the research challenges. There has been a lot of information, ideas, and principles presented over the course of this writing along with parallels to existing research and methodologies that can be almost directly applied to the concept of mapping security development to platform-based design. The primary cost of developing security, and running a secure system, is time. There are the monitary and hardware costs of security developement and implementation, but even those aspects all have a time cost coupled with them. Time, while being the most expensive part of security design is also the aspect that can be tackled and minimized with rigorous planning and documentation. Taking into account that even the development of documentation and standards also has its own time cost associated with it, this early phase development can also diminsh the time-cost impact for later steps in the system's development/implementation life-cycle. Security must be paramount in design from the very beginning of any design and developemtn cycle. \begin{itemize} - \item How to put cost on security? How to make models? What is high vs. low? (Are there models that exist?) + \item How to put cost on security? How to make models? What is high vs. low? (Are there models that exist?). While this paper proposes one model for security design and development this, by no means, is the only model for implementing security in a system. ``Defense in depth''~\cite{DoD2002} is a model in which security is derived from the application of multiple mechanisms; to create a series of barriers against attack by an adversary. Unfortunately, for the model, without any sound security architecutre and supporting theory, the non-constructive basis of this approach equivicates this model to a temporary patch; putting barriers in places does not equate to levels of trustworthiness. The ``Balanced assurance''~\cite{Lunt1988} model centers around a hierarchy of security policies, where different policies are allocated to different components of a system. The concept is that the trustworthiness of a given component must be consistent with the importance of that component's policy; the greater the trustworthiness the greater the importance of that component. The fault here is that a system can only be considered as secure as it's least secure component. While a interesting model and shows promise with respect to specific scenarios, this is not an overarching model that will function in all cases. + \item While there are multiple models for performing/implementing security, a significant part of the cost of building a secure system is that of evaluating, and subsequently proving, trustworthiness through a third party's efforts. A method for minimizing the costs of performing this evaluation is to make use of components that have already had their trustworthiness evaluated and verified, thereby minimizing the need to evaluate the system itself; as it is made of already trustworthy components. This model would allow for ``evaluation by pieces'' whereby one acknowledges previously evaluated components and does not require their examiniation in the greater evaluation of the composite system. Unfortunately, this model has only been made available to ``low assurance'' systems as it lacks a well-formed theory of correctness~\cite{Benzel2005}. \end{itemize} +\item Security design, development, verification, and evaluation is still a relatively new and unexplored space. Because of this there is a constant growth and evolution of security protocols and standards, which requires a thorough exploration of the security design space. It is the belief of this paper that the best model for focusing effort and development towards is a platform-based design for security development. The levels of abstraction aid in virtualization design, the overarching concept of mapping platforms to instances (and vica-versa) aids in early developemtn stages, and the need for rigorous documentation and meticulous following of standards are concepts that not only stem from platform-based design but greatly lend to the needs of security design and development. \end{itemize} \section{Conclusion} @@ -274,7 +246,7 @@ The issue of platform-based design is not so much an over-engineering of design/ \end{itemize} \item Advantages of security mapped to PBD: swap out old security modules with newer ones (re-use of base system), degree of system customization to meet system hardware/software needs, ease of development (and costs). \item As with any new shift in design methodoloy the largest cost in this new system would be the need for rigorous documentation and standardization of the process, components, and communication elements of said components. -\item This is why the development of groundwork for PBD-Security designs will be a slow and arduous work, but the resulting `paydirt' will be a new set of virtualization tools at abstraction levels with design spaces yet true explored at regualr levels. The hope of this paper is to begin designing a frame work that pushes for not only better system design and development (PBD) but also for proper incorporation and planning of system security in an intelligent, rigorous and documented/standardized way. +\item This is why the development of groundwork for PBD-Security designs will be a slow and arduous work, but the resulting `paydirt' will be a new set of virtualization tools at abstraction levels with design spaces yet not truly explored at regualr levels. The hope of this paper is to begin designing a frame work that pushes for not only better system design and development (PBD) but also for proper incorporation and planning of system security in an intelligent, rigorous and documented/standardized way. \item As with the design of any tool there are concerns during the development, evaluations and valdiation processes~\cite{Pinto2006}. Common pitfalls of development are mishandling corner cases and inadvertently misinterpreting changes in the communication semantics. Problems arise because of poor understanding and the lack of precise, rigorous, definitions of the abstraction and refinement maps used in the design flow. Abstraction and refinement should be designed to preserve, whenever possible, the properties of the design that have already been established (e.g. the 'contract' of the design). \item With these concepts in-mind, it should be obvious that security design \textbf{must} occur from the start! Unless security design is incorporated apriori, a developer can only hope to spend the rest of the development processes, and beyond, attempting to secure a system that took security as optional. \item The reference monitor seems a favorable choice as this sort of model is already used in distributed systems, but there is an extremely important need to maintain the security/trust/trustworthiness of this reference monitor (abstraction for necessary and sufficient features of component that enforces access controll in secure systems). It is the belief of this paper that an initial starting point for PBD-Security design development is to use this existing reference monitor concept, along with other developed tools (e.g. CBSE, TPM), and piece together the initial framework and early phase development for this new methodology, so that future efforts can be spent developing and perfecting this technique. @@ -426,6 +398,12 @@ url{https://embedded.eecs.berkeley.edu/metropolis/tools.html} \bibitem{CommonCriteria} ISO/IEC, \emph{ Common Criteria for Information Technology Security Evaluation}, ISO/IEC 15408 (July 2005) +\bibitem{DoD2002} Department of Defense, Directive 8500.1, \emph{ +Information Assurance (IA)}, 24 October 2002 + +\bibitem{Lunt1988} Teresa F.~Lunt, Dorothy E.~Denning, Roger R.~Schell, Mark Heckman, and W.~R.~Shockley, \emph{ +Element-level classification with AI assurance}, Computer and Security, 7:73-82, 1988 + \end{thebibliography} \end{document}