With licensing, what system parameters are referenced by the Trusted Storage licensing model?

Answer

The ArcGIS 10.x licensing model takes advantage of a licensing technology known as 'Trusted Storage'. The Trusted Storage model must both be initialized and associated with a specific system, and subsequently audited locally by the ArcGIS software platform for use.

Initialize and License Trusted Storage
The initialization step of the Trusted Storage model first submits at least one UMN (Unique Machine Number) to Esri, which is then assigned to generate a unique, machine-specific authorization. UMNs are based on values generated from the following machine parameters:

UMN 1: Boot disk Serial Number
UMN 2: Primary Ethernet Machine address (from first non-removable, non-virtual Ethernet device)
UMN 3: Virtualized SMBIOS UUID on hypervisors and Azure or the cloud virtual machine (CVM) Instance ID on Amazon EC2
UMN 5: GenerationID is a 128-bit value provided by the hypervisor to its VMs via the ACPI namespace of the virtual machine.

Warning:
The above values are based on the Windows operating system. They are utilized to generate the creation of the UMN number; the UMN number is the only machine-specific information that is sent to Esri.  The UMN number is used to assign an authorization to a specific machine. The actual UMN number is not decrypted to extract the above generated values. 

Trusted Storage Audit
Once initialized and licensed, the Trusted Storage remains on the local system and can be disconnected from the network indefinitely. At regular intervals, the Trusted Storage performs self-audits to ensure it has not been tampered with or copied.

If the Trusted Storage audit determines that the storage has either been copied, duplicated, or tampered, the Trusted Storage system becomes "untrusted" until a "repair" operation is initiated.

Repairing Trusted Storage
If Trusted Storage is in an "untrusted state" it must be repaired. Each license is allotted a set number of repairs to accommodate the vast majority of deployments under normal conditions.

If the Trusted Storage model becomes untrusted, a warning is received when launching ArcGIS Desktop, ArcGIS Administrator, or ArcGIS License Manager. The Trusted Storage can be repaired by clicking 'Repair' within the ArcGIS Administrator / ArcGIS License Administrator, or by de-authorizing and re-authorizing licenses.

Virtual Machines
Virtualized systems may be more dynamic than standard systems and may suffer more repairs than standard hardware-based deployments. For this reason it is recommended that physical machines be used with ArcGIS Desktop or ArcGIS License Manager to avoid this issue.

If a virtualized ArcGIS Desktop or License Manager is deployed, take special care to ensure it remains as static as possible by controlling factors such as the primary virtual drive, primary network interface card, and other virtualized adapters.

Virtualization technologies that result in significant changes to the overall system profile, such as imaging, ghosting, live migration and cloning, are all unsupported as they can invalidate the Trusted Storage model.