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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?

#91

Post by avianlyric »

timbre1234 wrote: post #72
avianlyric wrote: post #58

Somethings not mentioned in the article, but are pretty relevant. Modern SSD controllers encrypt all data by default. Not to increase security, to improve wear levelling. Encrypted data should be effectively random data (that’s what good encryption aims to produce). So encrypting the data ensures that patterns in data written to the SSD don’t end up creating uneven wear patterns in the flash chips. As a consequence,…

The problem with this is that erase-to-program delay is a major factor in bad write quality.....you really don't want to erase a block and wait a long time before programming it. Where "long" is subjective and there are a lot of details here but the general rule is that the longer you wait after an erase to write, the less accurate your write is (colloquially, your zero decays as it sits)......so in practice while yo…

Didn’t know that. Don’t suppose you’ve got any links that describe the physical process that results in the correlation between write quality and erase-to-program delay?

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

#92

Post by 13of40 »

amalcon wrote: post #78
bombcar wrote: post #49

Earlier quoted context omitted.

Hydraulic press is too obscure, .45 ACP works just as well. But it depends on your risk profile, for most people a wipe-and-reuse is going to be fine, especially if the "reuser" is already a trusted entity.

A firearm is a silly tool for this. A hammer (optionally combined with good nails) can do substantially the same thing to all relevant materials (aluminum, glass, ceramic, silicon, plastic), but cheaper and more safely.

I think a springloaded center punch to each of the chips would do a pretty good job of it.

https://www.harborfreight.com/spring-loaded-center-punch-621...

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

#93

Post by avianlyric »

gpderetta wrote: post #74
avianlyric wrote: post #58

Somethings not mentioned in the article, but are pretty relevant. Modern SSD controllers encrypt all data by default. Not to increase security, to improve wear levelling. Encrypted data should be effectively random data (that’s what good encryption aims to produce). So encrypting the data ensures that patterns in data written to the SSD don’t end up creating uneven wear patterns in the flash chips. As a consequence,…

But the "encryption" need not be cryptographic strength for this, so it might be reversible even without the key. Consider an old cypher with a small key for example.

Certainly true, but again, anyone that really cares about data destruction is never going to trust TRIM to destroy their data. At a minimum they’re going to use a mechanism that’s designed to destroy data (Secure Erase), and more likely they’re going to use multiple methods to destroy that data.

If you’re in a situation where you’re thinking that TRIM might be good enough, then you clearly don’t care that much about the data potentially being recovered by sophisticated attacker. You just don’t want it to be trivial to recover that data. In that case, even old cyphers and small keys is probably good enough.

But once again, if your really care about destroying your data, use something’s that’s explicitly designed to destroy data!

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

#94

Post by Dalewyn »

fdeee wrote: post #14
jsiepkes wrote: post #2

> Flash storage, unlike traditional hard drives, can really be completely and irrecoverably erased, with no lingering magnetic ghosts that a sufficiently determined person could in theory reconstruct. I think people vastly overestimate the possibility to recover any data from a wiped HDD. See for example this article by SANS [1]. To recover a single bit you have a better chance of flipping a coin to see if the bit wa…

I think you are right in that it is quite impossible to read data that has been overwritten from a sufficiently modern HDD. But all modern HDDs retire sectors that exhibit a higher correctable error rate and replace them by reserve sectors. Those retired sectors then still contain readable data (maybe with some bit errors) if you know the appropriate factory mode commands. Overwriting the entire disk also won't overw…

Or a low level format.

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

#95

Post by swagmoney1606 »

avianlyric wrote: post #91
timbre1234 wrote: post #72

Earlier quoted context omitted.

The problem with this is that erase-to-program delay is a major factor in bad write quality.....you really don't want to erase a block and wait a long time before programming it. Where "long" is subjective and there are a lot of details here but the general rule is that the longer you wait after an erase to write, the less accurate your write is (colloquially, your zero decays as it sits)......so in practice while yo…

Didn’t know that. Don’t suppose you’ve got any links that describe the physical process that results in the correlation between write quality and erase-to-program delay?

How hard would it be to write custom firmware for an M.2 SSD?

I'm not even sure where to start

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

#96

Post by vlovich123 »

avianlyric wrote: post #58

Somethings not mentioned in the article, but are pretty relevant. Modern SSD controllers encrypt all data by default. Not to increase security, to improve wear levelling. Encrypted data should be effectively random data (that’s what good encryption aims to produce). So encrypting the data ensures that patterns in data written to the SSD don’t end up creating uneven wear patterns in the flash chips. As a consequence,…

Do you have any pointers on where I can read this? It’s kind of the first I’m hearing that there’s encryption happening to side west leveling somehow and it’s not clear from a high level description why that would since west leveling is I thought a factor of write locations whereas encryption would only give you protection against bad bit patterns in what you write (but bit patterns afaik don’t impact wear on an SSD).

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

#97

Post by throw0101c »

avianlyric wrote: post #58

Somethings not mentioned in the article, but are pretty relevant. Modern SSD controllers encrypt all data by default. Not to increase security, to improve wear levelling. Encrypted data should be effectively random data (that’s what good encryption aims to produce). So encrypting the data ensures that patterns in data written to the SSD don’t end up creating uneven wear patterns in the flash chips. As a consequence,…

> Modern SSD controllers encrypt all data by default.

Contrary story from 2018/9:

> The security researchers explain that they were able to modify the firmware of the drives in a required way, because they could use a debugging interface to bypass the password validation routine in SSD drives. It does require physical access to a (internal or external) SSD. But the researchers were able to decrypt hardware-encrypted data without a password. The researchers write that they will not release any details in the form of a proof of concept (PoC) for exploit.

* https://borncity.com/win/2018/11/06/ssd-vulnerability-breaks...

> Microsoft is aware of reports of vulnerabilities in the hardware encryption of certain self-encrypting drives (SEDs). Customers concerned about this issue should consider using the software only encryption provided by BitLocker Drive Encryption™. On Windows computers with self-encrypting drives, BitLocker Drive Encryption™ manages encryption and will use hardware encryption by default. Administrators who want to force software encryption on computers with self-encrypting drives can accomplish this by deploying a Group Policy to override the default behavior. Windows will consult Group Policy to enforce software encryption only at the time of enabling BitLocker.

* https://msrc.microsoft.com/update-guide/en-us/vulnerability/...

> Although Windows ships with its own full volume encryption tool called BitLocker, SSDs that claimed to offer their own hardware-based encryption were trusted by the tool and left alone.

> Now though, after a recent update to Windows 10, Microsoft will assume that connected SSDs don't actually encrypt anything.

* https://www.techradar.com/news/microsoft-will-now-encrypt-ne...

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

#98

Post by fomine3 »

vlovich123 wrote: post #96
avianlyric wrote: post #58

Somethings not mentioned in the article, but are pretty relevant. Modern SSD controllers encrypt all data by default. Not to increase security, to improve wear levelling. Encrypted data should be effectively random data (that’s what good encryption aims to produce). So encrypting the data ensures that patterns in data written to the SSD don’t end up creating uneven wear patterns in the flash chips. As a consequence,…

Do you have any pointers on where I can read this? It’s kind of the first I’m hearing that there’s encryption happening to side west leveling somehow and it’s not clear from a high level description why that would since west leveling is I thought a factor of write locations whereas encryption would only give you protection against bad bit patterns in what you write (but bit patterns afaik don’t impact wear on an SSD)…

https://www.researchgate.net/publication/274369001_Data_secu...

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

#99

Post by Nursie »

cryptonector wrote: post #70
generalizations wrote: post #5

Or you encrypt the entire drive. Then the secure erasure is a matter of throwing away the keys, and you don't have to bother with thinking through your threat model.

Throwing away the keys is surprisingly hard to do. Say you have one root key and you derive per-file or per-block keys using various metadata (inode numbers, generation numbers, block addresses, whatever). You can't throw away derived keys though! Or say you generate random keys per-file and you store those somewhere (it's annoying to have to store them). Now to throw those keys away you need to re-write the blocks c…

> You can't throw away derived keys though!

You can, AES-XTS does just this. Per-block keys can be derived on the fly from the root key and the block address. When the root key is gone, everything is gone.

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

#100

Post by flangola7 »

MarkusWandel wrote: post #77
h2odragon wrote: post #41

https://en.wikipedia.org/wiki/Thermite Securely erases all known forms of electronic data storage. Cheap, reliable, fun for the whole family!

There was (is?) a type of hard disk where the platters are made out of glass. These are easy to dispose of securely... drop onto a concrete floor from about six feet up. Shake, feel finely pulverized glass rattling around inside. Done.

How do you magnetize glass?
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