FileVault Encryption for Mac Computers (macOS)

Original source: https://support.apple.com/guide/security/volume-encryption-with-filevault-sec4c6dc1b6e/1/web/1

Mac computers offerinclude FileVault, a built-in encryption capability,system tothat securesecures all data at rest.rest FileVault uses theusing AES-XTS dataencryption.

encryption

How algorithmIt toWorks

protect

On fullApple volumes on internalSilicon and removableT2 storage devices.Macs:

• FileVault on a Mac with Apple silicon is implemented usinguses Data Protection Class C with a volume key.key
On
• Encryption a Mac with Apple silicon and a Mac with an Apple T2 Security Chip, encrypted internal storage devices directly connected toleverages the Secure Enclave leverage its hardware security capabilities as well as that of theand AES engine.engine Afterhardware
a
• User usercredentials turnsrequired onat boot after enabling FileVault

Important: On older Macs (pre-T2), non-original internal storage, or external drives: Files created before enabling FileVault on a Mac, their credentials are required during the boot process.

Note: For Mac computers (1) prior to those with a T2 chip, or (2) with internal storage that didn’t originally ship with the Mac, or (3) with attached external storage: After FileVault is turned on, all existing files and any further data written are encrypted. Data that was added and then deleted before turning on FileVault isn’aren't encrypted and may be recoverable with forensic data recovery tools.

Internal storageStorage withSecurity

FileVault Enabled

When FileVault turnedis on

Without valid login credentials or a cryptographic recovery key, the internal APFSon, volumes remain encrypted and are protected from unauthorized access even if the physical storage devicedrive is removedremoved. andWithout connectedvalid tocredentials anotheror computer.a Inrecovery macOS 10.15, this includes both the system volume andkey, the data volume.is Startinginaccessible.

in

Encryption covers:

• macOS 11,10.15: theBoth system and data volumes
• macOS 11+: Data volume (system volume is protected by the signed system volume (SSV)feature)
feature,

but

Key theManagement dataApple volumeSilicon remainsand protectedT2 byMacs encryption. Internal volume encryption onuse a Machierarchical withkey Applesystem silicon as well as those with the T2 chip is implemented by constructing and managing a hierarchy of keys, and builds on the hardware encryption technologies built into the chip. This hierarchy of keys is designed to simultaneously achieve four goals:that:

Require

the
• Requires user’suser password for decryption
Protect
• Protects the system from aagainst brute-force attackattacks directly against storage mediaon removed fromstorage
Mac
• Enables Provide a swift andinstant secure method fordata wiping
content via deletion of necessary cryptographic material Enable users to change their
• Allows password (and in turn the cryptographic keys used to protect their files)changes without requiringfull reencryption
of the entire volume

On a Mac with Apple silicon and those with the T2 chip, all FileVaultAll key handlingoperations occursoccur inwithin the Secure Enclave; Enclave—encryption keys are never directly exposed toreach the Intel CPU. AllEach APFS volumesvolume are created withhas a volume encryption key by(VEK) default.that Volumeencrypts contents and metadatametadata. contentsThe are encrypted with this volume encryption key, whichVEK is wrapped withby a key encryption key (KEK)., The KEKwhich is protected by a combination ofboth the user’suser password and hardware UIDUID.

when

FileVault is turned on.

Disabled

InternalEven storagewithout with FileVault turned off

If FileVault isn’t turned on in a Mac withFileVault, Apple siliconSilicon or a Mac with theand T2 chip during the initial Setup Assistant process, the volume isMacs still encryptedencrypt volumes—but the volume encryption keyVEK is protected only by the hardware UIDUID. in the Secure Enclave.

IfEnabling FileVault later is turnedinstant on later—a process that's immediate because the (data has already beenencrypted) encrypted—and adds an anti-replay mechanism helpsto prevent the old hardware-only key (based on hardware UID only) from being usedused.

to

Secure decrypt the volume. The volume is then protected by a combination of the user password with the hardware UID as previously described.

Deletion

Deleting FileVault volumes

When deleting a volume, its volume encryption key is securely deleted bytriggers the Secure Enclave.Enclave Thisto helpssecurely preventerase its VEK, preventing future accessaccess. with this key even by the Secure Enclave. In addition,Additionally, all volume encryption keysVEKs are wrapped with a media key. The media key doesn’t provide additional confidentiality of data; instead, it’s designed to enable swift and secure deletion of data because without it decryption is impossible.

On a Mac with Apple silicon and a Mac with the T2 chip, the media key is guaranteed to be erased by the Secure Enclave supported technology—for example by remote MDM commands. Erasing the media key in(via thisMDM mannercommands, rendersfor example) makes the volume cryptographically inaccessible.

External Storage

Removable storagedrives devices

Encryption of removable storage devices doesn’don't utilize the security capabilities of theuse Secure Enclave,Enclave andcapabilities—they're its encryption is performed inencrypted the same mannerway as anIntel Intel-based MacMacs without the T2 chip.chips.