Hardware Architecture
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Time
35 hours 25 minutes
Difficulty
Advanced
Video Transcription
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>> Let's take a look a little bit
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closer at some of the elements that are in the TCB,
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starting with hardware architecture.
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Now, I want to be really clear,
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in this section,
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we're not going to get into the details
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of the different types of RAM or we're not going to get
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into anything really in-depth
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with processors or operating system kernels.
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We're going to just reference them.
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We'll talk about them at a high level.
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This exam, again, not a technical exam.
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If you're counting the pins on
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a processor or on a stick of memory,
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not the right test.
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We want to just understand is
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the elements of a TCB as they
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come together and really just
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understanding their role within a system.
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Don't go too deep here.
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Now when we start the elements of a system,
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the CPU is going to be the most
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significant because this is
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where all the processing happens.
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You're going to have registers which are areas of
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high-speed memory that store instructions
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the processors are going to need.
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We also have arithmetic logic units.
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There's control unit, there's math co-processor,
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they're just various elements that make
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up the processor that work together.
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We've got memory, different types of memory.
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We've got RAM and ROM.
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When we talk about buses,
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like the system bus,
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we're talking about the pathways on
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your motherboard that data can travel.
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Then of course, we have to think about storage.
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Now not all of
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these elements are part of the trusted computing base.
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Storage, for instance,
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your hard drive, optical drives,
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your solid-state drives,
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>> which are hard drives too often,
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>> but they can be magnetic or solid-state.
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Those are not elements of the TCB.
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If I was just looking at the TCB here,
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we'd focus on the processor and we'd focus on RAM.
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Now, focusing on the processor specifically,
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because the processor is one of
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the most trusted elements of a system,
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we've got to make sure that
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the processor is protected and is
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trustworthy and isn't compromised
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by rogue applications or services.
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The processor has two separate modes
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in which it can operate.
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One is called kernel mode
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and the other's called user mode.
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Now there's some other names for
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kernel mode could be called privileged mode,
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supervisor mode,
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but kernel mode is one that I
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hear most frequently I think.
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It's almost like if you're a network administrator,
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you don't come in at 8:30 in
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the morning and log on as network admin.
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Like I would come in and log in as Kelly Hindrahin,
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Kelly H, whatever my user account is.
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Then when I need to do
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administrative functions I would elevate my privilege.
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I don't just stay logged in all days and administrator.
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Well, neither does the processor.
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When a processor needs to perform elevated privileges,
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it escalates from user mode to kernel mode.
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Those escalated privileges are performed and
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then the processor operates back down to user mode.
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At that level, the default mode of
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user mode has less privileges.
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That even if there's some compromise of a service,
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then the damage is very limited.
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That's the CPU protection mode.
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Now, I'll just mention with RAM,
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the different types of RAM that we have.
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One of the things I'll mention is cache.
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Cache is an area of
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very high-speed memory for
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functions that are likely to be necessary,
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we have to make sure that cache is protected.
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Because if it does get modified,
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then users can be redirected to
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different resources and so on.
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We also have to think about virtual memory,
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which is a file actually stored on the hard drive,
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but it's designed to work like RAM.
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Because that hard drive isn't a trusted element, well,
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we have memory written to
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an untrusted element that can be an issue,
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so we're just aware of that for
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RAM and for memory in general.
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Like we said, storage
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isn't part of the trusted computing base.
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As a matter of fact, you don't even have to
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have storage devices on a system.
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I could boot up to some sort of external media,
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and I can store all my data in the Cloud,
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and a lot of systems are moving that way.
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Yeah, I think it's certainly as a technician,
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as a network admin,
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security admin to understand some of
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the different elements and how they come into play.
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But you don't need to get into the details here.
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I mentioned system buses,
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these are pathways and if you look at a motherboard,
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you can see the pathways on
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>> the board between components.
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>> Again, not an A-plus class,
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but I did feel like I ought
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to at least reference some of these hardware elements.
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Your system buses are not generally
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considered to be part of the trusted computing base.
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In this section, we covered the various elements of
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hardware and we said out of this four hardware,
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the CPU and memory are
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the most important elements
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of the trusted computing base.
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If either of those are compromised,
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then my system is compromised.
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