Hacker News Reader

Comment by Grimburger | Hacker News Reader

Most data is recoverable albeit slow to do. It takes some very bad conditions or intentional actions to make data recovery impossible. Current high level standards for military/diplomatic data sanatisation are complete physical destruction of hard disks.

Even linux tools like shred have given up saying they can actually delete data from disks due to how SSD's work these days.

View on HN

I don't agree - modern NVME drives have secure erasure mechanisms. All data is by default encrypted on-the-fly within the flash memory, and when requesting a secure erase, the controller throws away the key and generates a new one.

https://man.archlinux.org/man/nvme-format.1

In "reduce, reuse, recycle", this is the #2 R

Please don't trash physically good drives with a hammer. It's not good for the environment (or the drives!) when you have such a simple technology at your disposal!

What percentage of people on Earth use this in your expert opinion?

Also have you done any work in digital forensics?

Eagerly awaiting your response.

> I don't agree - modern NVME drives have secure erasure mechanisms.

Assuming the firmware doesn't lie about it does:

* https://www.zdnet.com/article/flaws-in-self-encrypting-ssds-...

> Even linux tools like shred have given up saying they can actually delete data from disks due to how SSD's work these days.

Which emphasizes the importance of enabling full disk encryption immediately whenever you start using a new device--BitLocker if you're on Windows, FileVault on macOS, LUKS on Linux, etc. Trying to decrypt data is much harder than reconstructing deleted data on a stolen drive.

True, properly zeroing out the headers on an encrypted drive will make recovery impossible.

How to do that reliably is another question.

You cannot with normal tools as writing a 0 to the SSD does not guarantee it overwrites the 0 you want. At best it does, at worst it writes the 0 somewhere else and remaps the bit (or whatever its physical storage thing is).

This is especially a problem on macOS:

https://support.apple.com/guide/disk-utility/erase-and-refor...

> Note: With a solid-state drive (SSD), secure erase options are not available in Disk Utility. For more security, consider turning on FileVault encryption when you start using your SSD drive.

So if you set up a Mac without FileVault you can never erase everything.

At least with my Lenovo I can do the secure erase.

SSDs are not magic. For shredding to be impossible the drives would have to have hidden capacity (and a lot of it, more than 1%). People often say, write levelling makes overwriting useless, but what if you overwrite the entire disk? How would you recover after something like this?

Of course providing something like 10% of hidden extra capacity would extend the life of the drive significantly, but are manufacturers really doing that and are not mentioning it in their marketing materials? I never heard that they do that.

Sure, but very few business tools are doing that, they are playing the old Gutmann game which he himself has walked away from as not reliable anymore. Filling up the drive is certainly getting you somewhere compared to some of the snake-oil out there. Drives are only getting bigger though and rarely filled up, done some of this stuff in my time and if cost is no barrier then you'd be surprised how much can be reclaimed. Degauss and destroy is the only real method we have now and that's probably not changing in future.

>but are manufacturers really doing that and are not mentioning it in their marketing materials

SSD manufacturers have been caught out repeatedly with their in-built deletion API claims. Recovery of a significant % of files is possible nearly always without tampering having occurred.

> Of course providing something like 10% of hidden extra capacity would extend the life of the drive significantly, but are manufacturers really doing that and are not mentioning it in their marketing materials? I never heard that they do that.

Every SSD has considerably more physical blocks than reported blocks. They have to, SSD bad blocks are common and number of writes is quite limited compared to hard disks.

https://download.semiconductor.samsung.com/resources/others/...

> I never heard that they do that.

Not sure how you missed it, as it's not a new thing. Straight from the horses mouth, if that helps: :)

https://www.kingston.com/en/blog/pc-performance/overprovisio...

Note that it's not just a Kingston thing, it's common across SSD manufacturers. Or at least with the major ones.

SSDs don't cycle blocks based on how much you've written. You can write over the entire reported capacity of a drive 100 times and there's still the chance, however small, that your encryption key and some encrypted data are still sitting around on some chip. You just can't guarantee that it's gone. For all you know, the controller has marked them as bad and isn't going to reuse them, even though there's still recoverable data on them. Since there's no way to reach them through the drive interface, there's also no way to erase them. But if someone opened up the drive and pulled the chips, there they would be.

> what if you overwrite the entire disk

People who want secure deletion generally want their storage device to remain functional afterwards. Same reason they don't simply destroy the disk to get rid of its contents: those things are expensive. Overwriting the entire SSD every time you want a file gone just isn't a solution.

Reply on news.ycombinator.com