en/security/trusty/index.html - platform/docs/source.android.com - Git at Google

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     <title>Trusty TEE</title>
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       Copyright 2017 The Android Open Source Project

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 <p>Trusty is a secure Operating System (OS) that provides a Trusted Execution
   Environment (TEE) for Android. The Trusty OS runs on the same processor
   as the Android OS, but Trusty is isolated from the rest of the system
   by both hardware and software. Trusty and Android run parallel
   to each other. Trusty has access to the full power of a device’s main
   processor and memory but is completely isolated. Trusty's isolation
   protects it from malicious apps installed by the user and potential
   vulnerabilities that may be discovered in Android.
 </p>

  <p>Trusty is compatible with ARM and Intel processors. On ARM systems,
    Trusty uses ARM’s Trustzone™ to virtualize the main processor and create
    a secure trusted execution environment. Similar support is also available
    on Intel x86 platforms using Intel’s Virtualization Technology.
 </p>

 <img style="display: block;margin-left: auto;margin-right: auto;"
      src="/security/images/trustyOverview_900w.png" />
 <p class="img-caption">
 <strong>Figure 1</strong>. Trusty overview diagram.
 </p>

 <p>Trusty consists of:</p>
 <ul>
   <li>A small OS kernel derived from <a
     href="https://github.com/littlekernel/lk" class="external">
     Little Kernel</a></li>
   <li>A Linux kernel driver to transfer data between the secure environment
     and Android</li>
   <li>An Android <a
     href="https://android.googlesource.com/trusty/lib/" class="external">
     userspace library</a> to communicate with trusted applications
     (that is, secure tasks/services) via the kernel driver</li>
 </ul>


 <p class="note"><strong>Note:</strong> Trusty and the Trusty API are subject
 to change. For information about the Trusty API, see the <a
 href="/security/trusty/trusty-ref">API Reference</a>.</p>

 <h2 id="whyTrusty">Why Trusty?</h2>

 <p>Other TEE operating systems are traditionally supplied as binary
   blobs by third-party vendors or developed internally.
   Developing internal TEE systems or licensing a TEE from a third-party
   can be costly to System-on-Chip (SoC) vendors and OEMs.
   The monetary cost combined with unreliable third-party systems creates an
   unstable ecosystem for Android. Trusty is being provided to its partners
   as a reliable and free open source alternative for their Trusted Execution
   Environment. Trusty offers a level of transparency that is just not possible
   with closed source systems.
 </p>

  <p>Android supports various TEE implementations so you are not restricted
    to using Trusty. Each TEE OS has its own unique way of deploying trusted
    applications. This fragmentation can be a problem for trusted application
    developers trying to ensure their apps work on every Android device.
    Using Trusty as a standard helps application developers to easily
    create and deploy applications without accounting
    for the fragmentation of multiple TEE systems. Trusty TEE provides developers
    and partners with transparency, collaboration, inspectability of code, and
    ease of debugging. Trusted application developers can converge around common
    tools and APIs to reduce the risk of introducing security vulnerabilities.
    These developers will have the confidence that they can develop an application
    and have it reused across multiple devices without further development.
 </p>

 <h2 id="application_services">Applications and services</h3>

 <p>A Trusty application is defined as a collection of binary files
   (executables and resource files), a binary manifest, and a
   cryptographic signature.
   At runtime, Trusty applications run as isolated processes in
   unprivileged mode under the Trusty kernel. Each process runs
   in its own virtual memory sandbox utilizing the memory management
   unit capabilities of the TEE processor. The build of the hardware
   changes the exact process that Trusty follows, but for example,
   the kernel schedules these processes using a priority-based,
   round-robin scheduler driven by a secure timer tick.
   All Trusty applications share the same priority.
 </p>

 <img style="display: block;margin-left: auto;margin-right: auto;"
      src="/security/images/trustyApps_900w.png" />
 <p class="img-caption">
 <strong>Figure 2</strong>. Trusty application overview.</p>

 <h2 id="third-party_trusty_applications">Third-party Trusty applications</h2>

 <p>Currently all Trusty applications are developed by a single
   party and packaged with the Trusty kernel image.
   The entire image is signed and verified by the bootloader during boot.
   Third-party application development is not supported in Trusty at
   this time. Although Trusty enables the development of new
   applications, doing so must be exercised with extreme care; each
   new application increases the area of the trusted computing base
   (TCB) of the system.
   Trusted applications can access device secrets and can perform
   computations or data transformations using them. The ability to
   develop new applications that run in the TEE opens up many
   possibilities for innovation. However, due to the very definition
   of a TEE, these applications cannot be distributed without some
   form of trust attached. Typically this comes in the form of a
   digital signature by an entity trusted by the user of the
   product on which the application runs.
 </p>

 <h2 id="uses_examples">Uses and examples</h2>

 <p>Trusted execution environments are fast becoming a standard in
   mobile devices. Users are relying more and more on their mobile
   devices for their everyday lives and the need for security is always
   growing.
   Mobile devices with a TEE are more secure than devices without a TEE.
 </p>

 <p>On devices with a TEE implementation, the main processor is often
   referred to as “untrusted”, meaning it cannot access certain areas
   of RAM, hardware registers, and write-once fuses where secret data
   (such as, device-specific cryptographic keys) are stored by the manufacturer.
   Software running on the main processor delegates any operations that
   require use of secret data to the TEE processor.
 </p>

 <p>The most widely known example of this in the Android ecosystem is the <a
   href="/devices/drm.html">DRM framework</a>
   for protected content. Software running on the TEE processor can
   access device-specific keys required to decrypt protected content.
   The main processor sees only the encrypted content, providing
   a high level of security and protection against software-based attacks.
 </p>

 <p>There are many other uses for a TEE such as mobile payments, secure banking,
   multi-factor authentication, device reset protection,
   replay-protected persistent storage, secure PIN and fingerprint processing,
   and even malware detection.
 </p>
   </body>
 </html>
	<html devsite>
	<head>
	<title>Trusty TEE</title>
	<meta name="project_path" value="/_project.yaml" />
	<meta name="book_path" value="/_book.yaml" />
	</head>
	<body>
	<!--
	Copyright 2017 The Android Open Source Project

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->
	<p>Trusty is a secure Operating System (OS) that provides a Trusted Execution
	Environment (TEE) for Android. The Trusty OS runs on the same processor
	as the Android OS, but Trusty is isolated from the rest of the system
	by both hardware and software. Trusty and Android run parallel
	to each other. Trusty has access to the full power of a device’s main
	processor and memory but is completely isolated. Trusty's isolation
	protects it from malicious apps installed by the user and potential
	vulnerabilities that may be discovered in Android.
	</p>

	<p>Trusty is compatible with ARM and Intel processors. On ARM systems,
	Trusty uses ARM’s Trustzone™ to virtualize the main processor and create
	a secure trusted execution environment. Similar support is also available
	on Intel x86 platforms using Intel’s Virtualization Technology.
	</p>

	<img style="display: block;margin-left: auto;margin-right: auto;"
	src="/security/images/trustyOverview_900w.png" />
	<p class="img-caption">
	<strong>Figure 1</strong>. Trusty overview diagram.
	</p>

	<p>Trusty consists of:</p>
	<ul>
	<li>A small OS kernel derived from <a
	href="https://github.com/littlekernel/lk" class="external">
	Little Kernel</a></li>
	<li>A Linux kernel driver to transfer data between the secure environment
	and Android</li>
	<li>An Android <a
	href="https://android.googlesource.com/trusty/lib/" class="external">
	userspace library</a> to communicate with trusted applications
	(that is, secure tasks/services) via the kernel driver</li>
	</ul>


	<p class="note"><strong>Note:</strong> Trusty and the Trusty API are subject
	to change. For information about the Trusty API, see the <a
	href="/security/trusty/trusty-ref">API Reference</a>.</p>

	<h2 id="whyTrusty">Why Trusty?</h2>

	<p>Other TEE operating systems are traditionally supplied as binary
	blobs by third-party vendors or developed internally.
	Developing internal TEE systems or licensing a TEE from a third-party
	can be costly to System-on-Chip (SoC) vendors and OEMs.
	The monetary cost combined with unreliable third-party systems creates an
	unstable ecosystem for Android. Trusty is being provided to its partners
	as a reliable and free open source alternative for their Trusted Execution
	Environment. Trusty offers a level of transparency that is just not possible
	with closed source systems.
	</p>

	<p>Android supports various TEE implementations so you are not restricted
	to using Trusty. Each TEE OS has its own unique way of deploying trusted
	applications. This fragmentation can be a problem for trusted application
	developers trying to ensure their apps work on every Android device.
	Using Trusty as a standard helps application developers to easily
	create and deploy applications without accounting
	for the fragmentation of multiple TEE systems. Trusty TEE provides developers
	and partners with transparency, collaboration, inspectability of code, and
	ease of debugging. Trusted application developers can converge around common
	tools and APIs to reduce the risk of introducing security vulnerabilities.
	These developers will have the confidence that they can develop an application
	and have it reused across multiple devices without further development.
	</p>

	<h2 id="application_services">Applications and services</h3>

	<p>A Trusty application is defined as a collection of binary files
	(executables and resource files), a binary manifest, and a
	cryptographic signature.
	At runtime, Trusty applications run as isolated processes in
	unprivileged mode under the Trusty kernel. Each process runs
	in its own virtual memory sandbox utilizing the memory management
	unit capabilities of the TEE processor. The build of the hardware
	changes the exact process that Trusty follows, but for example,
	the kernel schedules these processes using a priority-based,
	round-robin scheduler driven by a secure timer tick.
	All Trusty applications share the same priority.
	</p>

	<img style="display: block;margin-left: auto;margin-right: auto;"
	src="/security/images/trustyApps_900w.png" />
	<p class="img-caption">
	<strong>Figure 2</strong>. Trusty application overview.</p>

	<h2 id="third-party_trusty_applications">Third-party Trusty applications</h2>

	<p>Currently all Trusty applications are developed by a single
	party and packaged with the Trusty kernel image.
	The entire image is signed and verified by the bootloader during boot.
	Third-party application development is not supported in Trusty at
	this time. Although Trusty enables the development of new
	applications, doing so must be exercised with extreme care; each
	new application increases the area of the trusted computing base
	(TCB) of the system.
	Trusted applications can access device secrets and can perform
	computations or data transformations using them. The ability to
	develop new applications that run in the TEE opens up many
	possibilities for innovation. However, due to the very definition
	of a TEE, these applications cannot be distributed without some
	form of trust attached. Typically this comes in the form of a
	digital signature by an entity trusted by the user of the
	product on which the application runs.
	</p>

	<h2 id="uses_examples">Uses and examples</h2>

	<p>Trusted execution environments are fast becoming a standard in
	mobile devices. Users are relying more and more on their mobile
	devices for their everyday lives and the need for security is always
	growing.
	Mobile devices with a TEE are more secure than devices without a TEE.
	</p>

	<p>On devices with a TEE implementation, the main processor is often
	referred to as “untrusted”, meaning it cannot access certain areas
	of RAM, hardware registers, and write-once fuses where secret data
	(such as, device-specific cryptographic keys) are stored by the manufacturer.
	Software running on the main processor delegates any operations that
	require use of secret data to the TEE processor.
	</p>

	<p>The most widely known example of this in the Android ecosystem is the <a
	href="/devices/drm.html">DRM framework</a>
	for protected content. Software running on the TEE processor can
	access device-specific keys required to decrypt protected content.
	The main processor sees only the encrypted content, providing
	a high level of security and protection against software-based attacks.
	</p>

	<p>There are many other uses for a TEE such as mobile payments, secure banking,
	multi-factor authentication, device reset protection,
	replay-protected persistent storage, secure PIN and fingerprint processing,
	and even malware detection.
	</p>
	</body>
	</html>