On 13 Nov 2003, at 5:12, David Shayer wrote:
I was told that FileVault replaces your home directory with an encrypted disk image, much like PGP Disk, so its probably blockwise underneath the file system layer. Files in your home directory are copied into the disk image, and some file system links redirect calls to the home directory to the disk image, and keep the user from seeing it as another mounted disk.
This is basically correct. FileVault uses an auto-mounting version of the encrypted disk image facility that was in 10.2, tweaked to allow the image to be opened even before your main key chain is available (since the key chain is stored inside your home directory). The standard encrypted image format uses a random key stored on your key chain, which is itself encrypted with a salted and hashed copy of the keychain pass phrase, which defaults to your login password. My suspicion is that for the FileVault there is some other key chain file in the system folder which stores the key for decrypting your home directory disk image and that the pass phrase for that is just your login password.
File Vault will automatically expand or contract the disk image at certain points. It creates a new image, copies everything over, and deletes the old image.
Yup, it essentially does an "hdiutil compact" command when you log out.
I don't know what mode of AES-128 it uses.
I believe that it uses counter mode, since it's efficient when doing random access to the encrypted data. Nicko _______________________________________________ mac_crypto mailing list mac_crypto@vmeng.com http://www.vmeng.com/mailman/listinfo/mac_crypto --- end forwarded text -- ----------------- R. A. Hettinga <mailto: rah@ibuc.com> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/> 44 Farquhar Street, Boston, MA 02131 USA "... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'