Erase an SD card completely

[macstatic]

Is there a way to erase an SD memory card (connected to my Mac via a card-reader) completely without damaging the card? I don't want the new owner of the card to be able to recover old files on it.

And yes -I am aware of the "secure erase" option in Disk Utility, but understand that with multiple passes on a memory card (or SDD) you're basically shortening its lifespan considerably.

 

[Bruno09]

Hi,

you can encrypt the SD card (warning : not your internal hard drive !), then erase it.

See : https://support.apple.com/kb/PH21791?locale=en_US

 

[macstatic]

Good idea!
I didn't quite understand the part about choosing the startup disk though (marked in bold below):

1. In the Finder, open a window, press the Control key, then click the item you want to encrypt in the sidebar.

2. Choose Encrypt [item name] from the shortcut menu.

Choosing the startup disk turns on FileVault for your system.

It may take some time to encrypt, depending on how much information is stored on your Mac. However, you can use your Mac as usual while the disk is being encrypted.

.. so should I enable the (now encrypted) SD card as the startup disk? Obviously this won't work as it's a previously erased card for a digital camera.

 

[KALLT]

No, what Bruno meant is that you should convert or reformat the SD card as ‘Mac OS Extended (Journaled, Encrypted)’. However, doing so will waste write cycles as well. Doing a ‘zeroing’ secure erase is usually enough.

 

[macstatic]

Where do I find the zeroing secure erase option? In my Disk Utility (version 13/OSX 10.9.5), when I click on "Security options" I only get a slider where it ranges from "Fastest" to "Most secure". No mention of "Zeroing" anywhere as far as I can see.

 

[KALLT]

The scale should have a label underneath it. It should say something along the lines of ‘writing zeros to the disk’.

 

[macstatic]

Ah, got it! Here's a screenshot.
So basically this just fills up the memory card with zeroes until it's full? So the process won't reduce its life other than what filling it up with photos/videos or whatever would?

 

[Weaselboy]

The scale should have a label underneath it. It should say something along the lines of ‘writing zeros to the disk’.

I think you are thinking of older OS X versions. The newer versions are like this.

[doublepost=1483911248][/doublepost]

Ah, got it! Here's a screenshot.
So basically this just fills up the memory card with zeroes until it's full? So the process won't reduce its life other than what filling it up with photos/videos or whatever would?

Yes the effect is one write cycle like if you have filled the drive with files then deleted them.

 

[macstatic]

Oops!, sorry -I forgot to upload the screenshot (update: it's uploaded into the previous message now). Yes, I'm on 10.9.5.

So after writing a single cycle with zeroes like that it would have to take some (expensive) specialized service to recover anything on it and not just a regular OSX "undelete" tool like Disk drill, Data rescue, Photo rescue (and I few others which slipped my mind) to get them back?

 

[KALLT]

So after writing a single cycle with zeroes like that it would have to take some (expensive) specialized service to recover anything on it and not just a regular OSX "undelete" tool like Disk drill, Data rescue, Photo rescue (and I few others which slipped my mind) to get them back?

That is only possible if there is some over-provisioned part where some data might have survived the operation, but that would be a very small part, if it is at all present. Overwritten memory blocks are gone.