Refactor top-level document structure
In preparation for extending documentation on PSA certified and
secure processing environments, the top-level structure has been
cleaned-up and simplified. PNGs from tf-m for docs home have
been reused for consistency.
Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: Id2b7d9b46dd90f419d00c417a06003e32862ead0
diff --git a/docs/overview/example-usage.rst b/docs/overview/example-usage.rst
new file mode 100644
index 0000000..68422ba
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+Solving Common Security Problems
+================================
+
+The following are examples of how trusted services can solve common device security problems.
+
+
+Protecting IoT device identity
+------------------------------
+
+During the provisioning process, an IoT device is assigned a secure identity that consists of a public/private
+key pair and a CA signed certificate that includes the public key. The device is also provisioned with the
+public key corresponding to the cloud service that it will operate with. The provisioned material is used
+whenever a device connects to the cloud during the authentication process. To prevent the possibility
+of device cloning or unauthorized transfer to a different cloud service, all provisioned material must be
+held in secure storage and access to the private key must be prevented. To achieve this, the certificate
+verification and nonce signing performed during the TLS handshake is performed by the Crypto trusted service
+that performs the operations without exposing the private key.
+
+
+Protecting Software Updates
+---------------------------
+
+To ensure that software updates applied to a device originate from a legitimate source, update packages are
+signed. A signed package will include a signature block that includes a hash of the package contents within
+the signed data. During the update process, a device will verify the signature using a provisioned public key
+that corresponds to the signing key used by the update originator. By holding the public key in secure storage
+and performing the signature verification using the Crypto service, unauthorized modification of the update
+source is prevented.
+
+
+Secure Logging
+--------------
+
+A managed IoT device will often be configured by an installation engineer who has physical access to the
+device. To allow a cloud operator to audit configuration changes, it is necessary to keep a log of
+configuration steps performed by the installation engineer. To avoid the possibility of fraudulent
+modification of the audit log, a device signs log data using a device unique key-pair. The public key
+corresponding to the signing private key may be retrieved by the cloud operator to allow the log to
+be verified. To protect the signing key, the Crypto service is used for signing log records.
+
+--------------------
+
+*Copyright (c) 2020-2022, Arm Limited and Contributors. All rights reserved.*
+
+SPDX-License-Identifier: BSD-3-Clause