Ask HN: How secure is the encryption offered by OS X's Disk Utility?

Re:Ask HN: How secure is the encryption offered by OS X's Di... by 0x0 on Sunday June 18, 2017 @07:39PM (#14583630)

If encryption is moved from the block layer to the file layer (on a per-file basis), isn't there a risk of exposing unencrypted metadata such as filenames, file sizes, file modification times etc? Or applications accidentally making temporary (unencrypted) copies of files (perhaps in /tmp)? Or just by accidentally cat > 'ing a sensitive file into the wrong directory, thus accidentally leaving a plaintext copy around on the disk sectors? Am I wrong in thinking block level encryption is a comfortable safety net for preventing infoleaks for lost/stolen devices, since cleartext never hits the disk?

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Re:Ask HN: How secure is the encryption offered by OS X's Di... by jackjeff on Sunday June 18, 2017 @08:38PM (#14583824)

It really depends on the details of what the file system does. It is true that older file systems did not encrypt metadata but that's not the case for newer ones like ZFS or APFS.

The way I understand the scarce documentation about APFS is that all the metadata is encrypted with a disk key. But on top of that the file system encrypts user's files with a separate key.

So just like block level encryption plaintext never hits the disk.

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Re:Ask HN: How secure is the encryption offered by OS X's Di... by 0x0 on Sunday June 18, 2017 @08:54PM (#14583891)

That sounds great! Best of both worlds. Looking forward to see more details as the betas progress.

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Re:Ask HN: How secure is the encryption offered by OS X's Di... by tritium on Monday June 19, 2017 @12:20AM (#14584612)

If you've ever used Microsoft Windows Encrypting File System (EFS), you'd know that it's pretty much useless. The file table is not encrypted, exposing valuable details about user activity.

Sure, you can't read the contents of a file, but you sure do know a lot about what someone's been up to, by booting up your own system, while mounting their disk as a read-only slave.

You will see highly informative file names, file sizes, and all dates denoting creation, last access, last change, and owner. In a work environment, this means your boss can see a file like:

  C:\Users\User\Documents\i_hate_my_boss_but_my_boss_has_a_daughter_too_hot_to_give_up.txt (12KB, 2017-06-17 13:04:47)

Whoops! Forgot to delete that one!

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Re:Ask HN: How secure is the encryption offered by OS X's Di... by xxs on Monday June 19, 2017 @02:13AM (#14584891)

interesting:

  1) your name is 'User'
  2) you actually do use underscores instead of spaces
  3) any pics?

On a serious note: using archived/compressed files might be fine when one is aware about the shortcomings.

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Re:Ask HN: How secure is the encryption offered by OS X's Di... by eecc on Monday June 19, 2017 @02:33AM (#14584948)

I think every Filesystem entry is encrypted with its own random key and this is further encrypted with passphrase protected master key(s)

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