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As far as what I understand there are different approaches and I have a few doubts regarding each of them:

  • On the one hand, it seems that factory reset does not securely erase itself data from SSD storage for certain operating systems and devices. However, in case data are first encrypted and then the factory reset is executed, the data will remain in the storage as encrypted, thus they cannot be recovered (as long as the encryption scheme remain secure). My doubt is that this approach does take into consideration the fact that a portion of data may have been deleted before being encrypted, so they are not involved in the encryption once executed and they are recoverable. Is this a potential problem?

  • On the other hand, it seems that for SSD the traditional method of filling the whole storage with zeros or random data is not the reccomended approach because intense writing may reduce the life of the device and the reccomended approach is one exploting some magic related to the physics of the hardware that "erases" the electrons used to represent data at once. While the traditional method of filling the whole storage is not reccomended, is it still secure (as secure as the reccomended one)?

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  • Just partially, thanks however. – Lorenzo Mar 30 at 22:25
  • What do you mean by "partially"? What part of your question is not addressed is one of these 4 answers? – mentallurg Mar 30 at 22:26
  • While I get that it reduces the life of the device, I do not get how filling the whole storage is in terms of security with respect to the reccomended approach. – Lorenzo Mar 30 at 22:31
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    Then, as these answers suggest, start with naming your threats. Do you want to protect your erased data from some governmental or some other very powerful organization with huge resources? Then the most reliable way is to destroy the disk. Restoring of data after overriding is only possible in some specific cases and if an expensive equipment is used. If you want to protect erased data just from talented hackers, then even a single overriding of data will be sufficient. – mentallurg Mar 31 at 2:44
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A picture says a thousand words ...

Picture of an Apple smartphone that has been partially destroyed by burning

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Most trusted method of secure deletion in SSD is physical destruction. This include, incinerations, sheading...etc.

My doubt is that this approach does take into consideration the fact that a portion of data may have been deleted before being encrypted, so they are not involved in the encryption once executed and they are recoverable. Is this a potential problem?

Exactly yes. Encrypted data also recoverable but it is not readable. If your data is unencrypted it is possible to read. In addition to that SSD has built in secure deletion commands, unfortunately these commands are not fully trusted.

You can read this article and take advanced level knowledge about SSD sanitization. Additionally NIST 800-188 also provide comprehensive details about media sanitization.

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What about using a data recovery tool first, then encrypt everything and finally delete whatever you don't need? Thus, you'd make sure that whatever recoverable data your SSD has, will at least be encrypted.

Of course, the caveat to this approach is that one could use more sophisticated recovery tools than you and, thus, get access to unencrypted data you weren't able to recover.

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  • I believe it depends on the software for recovering you are using if the recovered data are simply unmarked as deleted or written in a new location. In the second case, the data may be still recovered. Moreover, recovering data requires a considerable effort and doing it may not be a good idea if the purpose is securely delete them instead. – Lorenzo Mar 30 at 22:49

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