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How secure is merely discarding (TRIMing) all of a SSD's blocks?

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Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#21

Post by kryps »

detrites wrote: post #15
germanier wrote: post #8

Earlier quoted context omitted.

This can't be true. Any method must be at least as good as a coin toss. If it's worse you can just bit flip the result and end up better than the coin.

Unbelievably, the paper actually makes that claim: > That is, if you toss a coin, you have a 50% chance of correctly choosing the value. In many instances, using a MFM to determine the prior value written to the hard drive was less successful than a simple coin toss. More believably, the paper was written by Dr Craig Wright.

The paper does not make that claim. According to the paper the probability of recovering the correct value of a single bit is 96% for a pristine drive and 56% for a used drive, both better than a coin toss. Of course the probability gets worse if one tries to recover more bits (but still better than n coin tosses for n bits).

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#22

Post by tracker1 »

If security is your biggest concern, and not reuse... then using industrial shredding machinery is your best bet.

If you want reuse... then a handful of fill/erase cycles with random data is probably your best bet, even then, there will still likely be some overprovisioned blocks with prior data.

Encryption and throwing away the key doesn't do more than random data to fill said drive.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#23

Post by dark-star »

I'm surprised people actually think TRIMming is in any way a "secure delete" operation.

It's basically the "quick format" of SSDs: "hey, all those blocks here, I don't care about them anymore, use them as if they were free..."

Without OS-side encryption, Secure Erase is the only reliable option (SSD encrypts everything with an internal key which then gets deleted by the secure erase command, leaving only random data behind)

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#24

Post by hedora »

bshipp wrote: post #11
fdeee wrote: post #7

Earlier quoted context omitted.

The only proper way of disposal is physical destruction, preferrably on site and under observation of inhouse staff. There are contractors you can hire in those: https://shredsupply.com/hard-drive-shredding-trucks/ (no relation, just arbitrary google hit). I'm also unsure as to why you are getting drives back at all, any of your customers should not have any kinds of storage devices leave their site intact. At least…

Shredding/sledgehammer is likely the best option for secure disposal of mechanical drives, but SSDs are a different animal and are likely reusable given some of the suggestions in this thread.

Most hard disks support hardware level encryption and full disk erase at this point.

There’s very little need to sledgehammer anything given realistic attacker models.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#25

Post by h506001 »

SirGiggles wrote: post #9
h506001 wrote: post #3

Super interested in this and would love to hear about some techniques. Used to work at a HealthTech co. We had an “appliance” that we’d send to doctor offices to integrate with other diagnostic machines on the network. Sometimes we would send out new ones to replace the old. When we got the old ones back, it was always unclear how to purge and recommission SSD/NVME drives. My best attempt was using GNU shred, but it…

In addition to the sibling comment, I'm surprised that there was no mention of FDE.

We did do some encryption with LUKS, and I’d try to write over boot records, keys, and headers, but I was pessimistic that was enough. Not an encryption expert myself. Always felt that any given encryption tech (be it hardware or software) has possibility of vulnerability later found or backdoors.

So it made sense to me that a physical erasure prior to recommission would be good. There’s also regulatory/compliance checkboxes (be them effective or not).

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#26

Post by hedora »

Nursie wrote: post #16
h506001 wrote: post #3

Super interested in this and would love to hear about some techniques. Used to work at a HealthTech co. We had an “appliance” that we’d send to doctor offices to integrate with other diagnostic machines on the network. Sometimes we would send out new ones to replace the old. When we got the old ones back, it was always unclear how to purge and recommission SSD/NVME drives. My best attempt was using GNU shred, but it…

Buy SSDs with secure erase (many of them!), they encrypt data internally. Secure-erase the throws away the key, and all the data is now irretrievable. Job done…

I take your standard, solder it to a motherboard, and disable it with a TPM protected bios.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#27

Post by marginalia_nu »

detrites wrote: post #15
germanier wrote: post #8

Earlier quoted context omitted.

This can't be true. Any method must be at least as good as a coin toss. If it's worse you can just bit flip the result and end up better than the coin.

Unbelievably, the paper actually makes that claim: > That is, if you toss a coin, you have a 50% chance of correctly choosing the value. In many instances, using a MFM to determine the prior value written to the hard drive was less successful than a simple coin toss. More believably, the paper was written by Dr Craig Wright.

Right, if you flip a hundred coins, about half of them land heads and the other half tails. The correct coins we'll call oracles, and the incorrect ones liars.

Now you perform a hdd recovery that is successful 70% of the time. That is still worse than the performance of the oracle coins which were correct, and if you invert the performance of the liars, they also beat the performance of the recovery.

If you have two coins, one which is always correct and one which is always incorrect, you can flip one of them to decide whether the other one is correct (and pick the opposite).

Check mate, statisticians!

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#28

Post by beardog »

Nursie wrote: post #16
h506001 wrote: post #3

Super interested in this and would love to hear about some techniques. Used to work at a HealthTech co. We had an “appliance” that we’d send to doctor offices to integrate with other diagnostic machines on the network. Sometimes we would send out new ones to replace the old. When we got the old ones back, it was always unclear how to purge and recommission SSD/NVME drives. My best attempt was using GNU shred, but it…

Buy SSDs with secure erase (many of them!), they encrypt data internally. Secure-erase the throws away the key, and all the data is now irretrievable. Job done…

If you trust that the secure erase part of the firmware functions properly. There was work in the last 5 years to let the OS (at least Linux) do most of the SSD controller functionality which I think would be helpful if it caught on.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#29

Post by fdeee »

bshipp wrote: post #11
fdeee wrote: post #7

Earlier quoted context omitted.

The only proper way of disposal is physical destruction, preferrably on site and under observation of inhouse staff. There are contractors you can hire in those: https://shredsupply.com/hard-drive-shredding-trucks/ (no relation, just arbitrary google hit). I'm also unsure as to why you are getting drives back at all, any of your customers should not have any kinds of storage devices leave their site intact. At least…

Shredding/sledgehammer is likely the best option for secure disposal of mechanical drives, but SSDs are a different animal and are likely reusable given some of the suggestions in this thread.

Not really. HDD recoverability is a myth, anything overwritten isn't coming back with modern HDDs. Bits can't "bleed out" anymore, density is far too high for that.

The thing you need to guard against is relocated/reserve sectors, in HDDs same as in SSDs. The proper way to do this is full disk encryption, and if that's not possible, physical destruction.

Re: How secure is merely discarding (TRIMing) all of a SSD's blocks?

#30

Post by ChoGGi »

LinuxBender wrote: post #12

As others have mentioned, use encryption. But that has gaps as someone can hold onto the drive and wait for impossible to break to become somewhat expensive to break to broke by mistake through bad encryption implementation . Put the encrypted drive into a hydraulic press and flatten it into a thin sheet, then run that sheet through a chop saw, or just use tin-snips if your hydraulic press was powerful enough. A hydr…

I think an angle grinder would be more accessible than a press.
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