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9 Dell PS Series Architecture: Self Encrypting Drive Management with PS Series Storage Arrays | TR1093
3 Securing data with SED technology on PS Series arrays
As the leader in storage technologies, Dell EMC provides support and management capabilities that allow
users to safely secure their data-at-rest in PS Series arrays. This support is offered through AutoSED which
combines local key management with SEDs. The Dell AutoSED feature provides the all of the benefits of SED
security with no special effort on the part of the administrator. An administrator does not need to configure or
set up drives, manage encryption, install a Key Management Service (KMS) or ever issue an instant secure
erase command. Everything is handled by AutoSED as it is a completely self-contained keying system.
The AutoSED feature is embedded within the PS Series firmware version 6.0 and above. As said above, it
does not need to be separately installed. When a PS Series array equipped with SEDs is first powered on, the
AutoSED feature immediately engages and begins providing data at rest protection.
3.1 Key management
AutoSED relies on the concept of cryptographic secret sharing as discovered by Adi Shamir. This allows an
AutoSED array to unlock itself without revealing the key.
The concept of a SEDset is central to the AutoSED security model. Similar to how RAID groups hard drives
into a RAID set for redundancy, AutoSED groups hard drives into a SEDset for security. There is always one
SEDset per PS Series member equipped with SED drives, spanning all active drives in the member. The
SEDset cannot be unlocked unless it is sufficiently intact. A SEDset is considered intact when at least half of
its drives are present (excluding spares, failed, and foreign drives).
The access key is the key that is protected by AutoSED. When a SED PS Series member is initially
configured, AutoSED configures a small unsecured band for drive labels, followed by a single secured band
spanning the rest of the drive. AutoSED then generates a new and unique AK using a randomized function.
Every drive in the array will be locked with this one AK. AutoSED then uses the Shamir algorithm to split the
AK into multiple pieces, called shares. AutoSED always chooses to split the key such that one share is written
to each of the active drives in the system in the unsecure band on that drive. AutoSED requires that at least
half of its drives to be functioning in order to reassemble the AK.
3.2 Instant Secure Erase (ISE)
With AutoSED, a user does not ever issue a secure erase command. If a member is removed from the group
– for example, to be repurposed for the use of some other department in a different PS Series group – then
the ISE function is invoked on all of the drives in the array, causing all of the MEKs to be regenerated, and
whatever data was once on the array is no longer accessible. As discussed above, ISE is also invoked when
a failing drive is removed from service by the PS Series firmware before it is marked failed. Drives that fail
suddenly, without warning, do not undergo ISE, but are still safe to return since they are still in a locked state
and the data cannot be recovered.
Cases when ISE is invoked:
 Array reset (all drives undergo ISE)
 Disk mirror/copy-to-spare (the original drive gets erased by ISE when the copy process is done)