Editing FileVault (section)

==FileVault 2==
===Security===
FileVault uses the user's login password as the encryption passphrase. It uses the [[Disk encryption theory|XTS-AES]] mode of [[Advanced Encryption Standard|AES]] with 128 bit blocks and a 256 bit key to encrypt the disk, as recommended by [[NIST]].<ref name="wpfv2" /><ref>{{cite journal | url=http://csrc.nist.gov/publications/nistpubs/800-38E/nist-sp-800-38E.pdf | title=Recommendation for Block Cipher Modes of Operation: The XTS-AES Mode for Confidentiality on Storage Devices | author=Dworkin, Morris | journal=NIST Special Publication |date=January 2010 | issue=800–3E| doi=10.6028/NIST.SP.800-38E }}</ref> Only unlock-enabled users can start or unlock the drive. Once unlocked, other users may also use the computer until it is shut down.<ref name=aboutfv2 />

===Performance===
The [[I/O]] performance penalty for using FileVault 2 was found to be in the order of around 3% when using CPUs with the [[AES instruction set]], such as the [[Broadwell (microarchitecture)|Intel Core i]], and [[OS X Yosemite|OS X 10.10.3 Yosemite]].<ref>{{cite web |url=https://archive.techarp.com/showarticle0037.html?artno=877&pgno=1 |website=Tech ARP |title=How Fast is the 512 GB PCIe X4 SSD in the 2015 MacBook Pro?}}</ref> Performance deterioration will be larger for CPUs without this instruction set, such as older [[Intel Core (microarchitecture)|Core]] CPUs.

===Master passwords and recovery keys===
When FileVault 2 is enabled while the system is running, the system creates and displays a recovery key for the computer, and optionally offers the user to store the key with Apple. The 120 bit recovery key is encoded with all letters and numbers 1 through 9, and read from {{mono|/dev/random}}, and therefore relies on the security of the [[Pseudorandom number generator|PRNG]] used in macOS. During a cryptanalysis in 2012, this mechanism was found safe.<ref name=choudary2012>{{cite journal|last=Choudary|first=Omar|author2=Felix Grobert |author3=Joachim Metz |title=Infiltrate the Vault: Security Analysis and Decryption of Lion Full Disk Encryption|date=July 2012|url=http://eprint.iacr.org/2012/374|access-date=January 19, 2013}}</ref>

Changing the recovery key is not possible without re-encrypting the File Vault volume.<ref name="aboutfv2" />

===Validation===
Users who use FileVault 2 in OS X 10.9 and above can validate their key correctly works after encryption by running {{mono|sudo fdesetup validaterecovery}} in Terminal after encryption has finished. The key must be in form {{mono|xxxx-xxxx-xxxx-xxxx-xxxx-xxxx}} and will return true if correct.<ref>{{cite web | url=https://developer.apple.com/library/Mac/documentation/Darwin/Reference/ManPages/man8/fdesetup.8.html | title=fdesetup(8) Mac OS X Manual Page | publisher=[[Apple Inc.|Apple]] | date=August 21, 2013 | access-date=August 9, 2014}}</ref>