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Home<br>> Apple File System, Apple Silicon, FileVault 2, Mac administration, macOS > FileVault on versus off on Apple Silicon Macs

FileVault on versus off on Apple Silicon Macs

July 18, 2026<br>rtrouton Leave a comment<br>Go to comments

I recently gave a talk on how FileVault works on Apple Silicon Macs running macOS Tahoe. As part of doing the research for it, one of the things which stood out to me is how Apple has designed encryption at rest protection for Apple Silicon Macs. If you’re using an Apple Silicon Mac, most of those protections are enabled out of the box for you even if you’re not using FileVault. That’s not me saying to skip enabling FileVault, it’s a recognition of how much work Apple has put into making sure that its devices are protected regardless of the device owner’s decision making. For more details, please see below the jump.

Every Apple Silicon Mac comes equipped with the following:

Hardware encrypted internal SSD

Secure Enclave

AES Engine built into the data path between the SSD and main memory

At the Secure Enclave’s manufacturing time, two keys are created:

Hardware key :

Unique identifier for device

Generated by the Secure Enclave’s own true random number generator.

Written to on-chip fuses through a process that runs entirely within the Secure Enclave.

This ensures the UID is never exposed outside the device and is not accessible to Apple, its suppliers, or anyone else.

xArt key

Generated by xART (eXtended Anti-Replay Technology) – a set of services built into the Secure Enclave specifically to prevent replay attacks.

Created as a random number

Both keys combine to form the Volume Encryption Key (VEK) that protects the data on the internal SSD’s APFS storage. All three keys stay resident entirely within the Secure Enclave and never leave it.

The AES Engine is then used to handle the encryption and decryption of data. This component is tied to the Secure Enclave using a dedicated isolated hardware connection, which allows the Secure Enclave to securely supply the AES Engine with the required keys. As mentioned earlier, the AES Engine sits directly on the data path between the SSD and main memory. This allows the following:

Data stored on the SSD flows into the AES Engine before going to main memory.

The AES Engine handles decryption, using keys supplied by the Secure Enclave, before sending data to memory.

Data stored in memory flows to the AES Engine before going to the SSD.

The AES Engine handles encryption, using keys supplied by the Secure Enclave, before sending data to the SSD.

With FileVault not enabled, the key structure looks like this:

What happens when FileVault is not enabled?

Secure Enclave generates a Volume Encryption Key (VEK) using the Hardware key and the xArt key

Hardware key is provided automatically by the Secure Enclave to unlock the VEK at the Mac’s boot time.

Effective outcome

Data stored on the internal SSD is protected against access in the event that the drive is removed and someone tries to read it.

The Hardware key is required to unlock the drive’s encryption and that key is only stored in that specific Mac’s Secure Enclave.

There are no additional authentication steps needed to unlock the encryption.

This sounds like decent protection by itself, but Apple strengthens it further when you turn on FileVault. What happens when FileVault is enabled?

Before you turn on FileVault:

Internal SSD is already encrypted

VEK is protected only by the Hardware key

When you turn on FileVault:

Your account’s password is used to create a derived key.

The key derived from your account’s password is sent into the Secure Enclave and combined with the Hardware key to create a new Key Encryption Key (KEK).

A new VEK is generated, with the KEK used to unlock the VEK

This means that the VEK protecting the SSD’s data moves from one protected only by the Hardware key to one now protected by a combination of the derived key from the user’s password and the Hardware key.

The existing VEK (which was protected only by the Hardware key) is invalidated.

The xART anti-replay protections ensure that the previous VEK can’t be used later to unlock the encryption.

A recovery key is created in the form of a 24 character random alphanumeric string. This is a derived key similar to the one generated from your user account’s password and the KEK is rewrapped to allow this derived key to also unlock the KEK (and thus the VEK.)

Note: All keys involved and their handling, with the exception of the derived keys created from the user account’s password and the recovery key, stay entirely within the Secure Enclave.

With FileVault enabled, the key structure now looks like this:

Effective outcome

Unlocking the Mac’s data encryption changes from using something inherent to the Mac (the Hardware key) to also now requiring...