How to *safely* sell a Mac with an SSD or Fusion Drive?

Discussion in 'iMac' started by ace8cjc, Feb 27, 2015.

  1. ace8cjc macrumors newbie

    Feb 27, 2015
    Hi all -

    My apologies if I'm posting this in the wrong group. Please re-direct me if I am.

    As I'm sure most of you know, you can't Secure Erase an SSD or Fusion Drive like you would an HDD. I've read the science behind why that's the case, but this seems like a huge security (and reseller) problem for people who intend to sell their old macs and buy new ones in the coming years.

    If we can't securely erase our drives, how can we expect to sell these computers with peace of mind? With essentially all new Mac's coming with an SSD or Fusion Drive, it seems like we'll all be in the same boat sooner or later.

    My question is, how are you all selling your SSD or Fusion Drive Macs in a relatively safe manner? I know that it's near impossible to to guarantee 100% data erasure, but I'm curious what others are doing and where they are drawing the line.

    I'd currently like to sell an iMac with a Fusion Drive.

    I've read about encrypting your SSD via FileVault and essentially throwing away the key, but i've also read that FileVault can easily be cracked now?

    Seems there are other ways to wipe the data, but they may greatly reduce the life of the SSD or Fusion Drive - which I don't think is fair if I intend to sell it shortly after. I'm an honest salesman I guess.

    Thanks in advance.
  2. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Now sure what you read, but I have never seen anything about anybody being able to crack FileVault. I would just turn on FV2 and encrypt, then go to Internet recovery and erase the drive and reinstall.
  3. Alesc macrumors 6502


    Nov 11, 2014
    Before FileVault2, before selling my machines, I used to format the drive, clean install the OS and erase the free space of the disk (with Drive Utilities).
    Now, I'm using FileVault2, so a clean install is enough.
    And I don't think FileVault2 is crackable... It is a full encryption of the disk, it is far more reliable than the previous FileVault.
  4. ace8cjc thread starter macrumors newbie

    Feb 27, 2015
    Thanks for the quick replies already.

    For what it's worth, here is where I read about FileVault2 being crackable:

    Granted, we're talking about a $1K piece of software here, and perhaps this means that the clean install will remove the key from memory?

    "The technique requires certain conditions to work, starting with the computer being turned on and logged in; the FileVault, BitLocker or TrueCrypt keys have to be in memory for Passware Kit Forensic to be able to extract them.

    Put another way, the product cannot extract encryption keys on static data or before the keys have been summoned as part of the logging-in process. As long as the login is not automatic users should be safe."
  5. imaccooper macrumors regular


    May 29, 2014
    North Carolina
    I'm not trying to be funny here, but if it is something that is really going to bother you then you can just buy a new SSD and put it in the machine you are going to sell.

    You definitely won't make your money back on the sale, but it is possible that someone might pay a little extra for a brand new SSD.

    Again, I'm not being funny, but if it is something that you think will bother you then that is a way you can be sure.
  6. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    That is really old info. That technique uses direct memory access (DMA) to access the encryption keys, and that was patched in Lion 10.7.2. It is no longer an issue.
  7. ace8cjc thread starter macrumors newbie

    Feb 27, 2015
    Gotcha - well, I appreciate yours (and everyone's) info. Sounds like FV2 encryption, erase, and reinstall is the way to go.

  8. Chippy99 macrumors 6502a

    Apr 28, 2012
    Yes you can and I have done it several times. You need to issue an ATA-Secure Erase command to the drive controller, which then sends an electrical impulse to wipe all of the NAND cells completely. All SSD's support this.

    The difficult part is how to issue the command with an iMac. The answer is to boot a linux image and do it from there. Fortunately such a bootable image, with the appropriate ATA Secure Erase tool already installed, can be found here:

    It used to be free, but sadly they now charge $9 for it.

    This is what Kingston have to say about it:

    ATA Secure Erase is part of the ATA ANSI specification and when implemented correctly, wipes the entire contents of a drive at the hardware level instead of through software tools. Software tools over-write data on hard drives and SSDs, often through multiple passes; the problem with SSDs is that such software over-writing tools cannot access all the storage areas on an SSD, leaving behind blocks of data in the service regions of the drive (examples: Bad Blocks, Wear-Leveling Blocks, etc.)

    When an ATA Secure Erase (SE) command is issued against a SSD’s built-in controller that properly supports it, the SSD controller resets all its storage cells as empty (releasing stored electrons) - thus restoring the SSD to factory default settings and write performance. When properly implemented, SE will process all storage regions including the protected service regions of the media.

    Secure Erase is recognized by the U.S. National Institute for Standards and Technology (NIST), as an effective and secure way to meet legal data sanitization requirements against attacks up to laboratory level. Kingston SSDNow drives support the ATA Security Command for proper data sanitization and destruction.
  9. Chippy99 macrumors 6502a

    Apr 28, 2012
    I forgot to add, that above is the best method.

    Other methods - such as encrypting the drive, or writing zeros all over it like a Mac Disk Utility does, will NOT destroy the on the entire drive! This is because SSD's have spare capacity and use wear-levelling to increase the drive lifespan. What the OS sees is only the logical portion of the drive that the SSD controller chooses to show, i.e. there are hidden physical blocks that may contain copies of your data and which any software-based wipe will be unable to touch.

    It is not easy to access the data in these hidden blocks, but it's not impossible. So you are probably secure, but it depends how safe you want to be. The FBI or perhaps even the regular police could retrieve this data if they wanted to.

    The ATA-Secure-Erase, wipes the ENTIRE SSD, including the hidden blocks.
  10. ace8cjc thread starter macrumors newbie

    Feb 27, 2015
    Gotcha - thanks for the info. Do you know if Parted Magic will work okay with an iMac Fusion Drive where both an HDD and SSD are used and presented as a single logical drive? I don't want to break that relationship, and once I've re-installed the OS, I'd like for the two drives to still work together as a Fusion drive.
  11. Fishrrman macrumors G5


    Feb 20, 2009
    You may have to

    1. "Split apart" the fusion drive into "standalone" SSD and HDD

    2. Use Parted Magic to do the secure erase, and then

    3. "Re-fuse" the two drives into a "fused" volume (Disk Utility should be able to do this for you), then

    4. Do a clean system software install.

    A good amount of work, but if you're that concerned about securely erasing what was on the disk, there may not be any other choices...
  12. Chippy99 macrumors 6502a

    Apr 28, 2012
    Honestly, I don't know. I don't know enough about how Fusion works.

    But I would *imagine* that Linux will see the two drives (SDD and HDD) as being completely seperate drives and will allow you to wipe either the SSD or the HDD or both. (There's regular disk-wiping capability in Parted Magic as well as the ATA-Secure-Erase command).

    The question is, if you wipe both drives in Linux like this, what happens to the "Fusion" drive? I don't know whether you'd need to rebuild in OS X or not.
  13. ace8cjc thread starter macrumors newbie

    Feb 27, 2015
    So! In case anyone is interested, here is what I did and it worked beautifully.

    1) Burned Parted Magic to a CD and booted from that (holding "c" during the boot sequence).
    Note - I originally created a Parted Magic LiveUSB, but my iMac wouldn't recognize or boot from it. I did some research, and apparently other people have had the same issue. I recommend the LiveCD.

    2) Once in Parted Magic, I opened the application "Erase Disk" on the desktop, which recognized both the SSD and HDD as separate drives (despite that I did not break apart the Fusion Drive). I issued an internal "Secure Erase" command against the SSD, as well as a physical (dd) erase command against the HDD. I also issued an internal "Secure Erase" command against the HDD, although I'm not sure how that differs between HDD and SSD. In any case, the Parted Magic documentation says it's supported.

    3) With the disks erased, I rebooted into Apple Internet Recovery (command+r). I first opened Disk Utility, which flagged both drives as having an issue. However, here is the cool part: It still knew that they were supposed to be a Fusion Drive and offered to repair it. One click and it was back to being a Fusion Drive in a few seconds.

    4) Still in Internet Recovery, I re-installed Mac OS X to the Fusion Drive.

    5) Once re-installed, I ran Apple Diagnostics which returned with "no issues found"

    In all, it was very painless. I'm sure that encrypting the disk and reformatting would have been enough security, but this way, I know with absolute certainty that my data is gone. From what I understand, there is no coming back whatsoever from an ATA Secure Erase.

    The usual disclaimer: This worked for ME, but I in no way state that this will work for anyone else. Try at your own risk.

    Thanks everyone for your help!
  14. Chippy99 macrumors 6502a

    Apr 28, 2012
    Cool :)

    Glad to hear it worked for you. Strange you couldn't get the USB stick to boot - I have Parted Magic on a USB stick and it boots just fine. (Don't ask me how I did it mind you - it was ages ago!)

    Presumably you had to put your Mac to sleep to unlock the SSD? I had to, but it all worked just fine.
  15. ace8cjc thread starter macrumors newbie

    Feb 27, 2015
    Yep, exactly. I put it to sleep via the application, brought it back up by tapping a few keys, and it was unlocked.

    I also found that Parted Magic wouldn't recognize the Bluetooth keyboard, however, it would recognize the Bluetooth mouse!
  16. Chippy99 macrumors 6502a

    Apr 28, 2012
    Ah, I have a wired keyboard so never noticed this!
  17. fbx1989 macrumors newbie


    Aug 7, 2017
    Hello Hello--

    This was two years ago now, but I'm wondering if it's still a viable method for 2017 iMac 5K? Or if there's an easier way to safely clean an iMac for return.

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