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Unsure if I'm asking this in the right place but here goes:

Security by Obscurity is the process of making data so obscure it therefore becomes secure as no one can read/understand it.

My question is what is the "term" for deleting data in order to make sure it is secure (i.e. deleting old e-mails)? I understand deleting could be argued as obscuring the data, but is this the correct term?

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I'm not sure there is such a term or there would be any purpose for such a term. It's definitely not the same as "security by obscurity" - since obscurity would imply it exists. –  NickC Dec 15 '10 at 15:50
Deleting data is not obscuring data it is deleting it. Obscuring data is obscuring data. –  Chris Dec 15 '10 at 18:41
That's not really security by obscurity. Security by obscurity implies that you simply hide the data, but that it is always here somewhere and (more or less directly) available, and that your first line of defense is simply to not explicitly "look, my data is here" or "my data is like this". It's a common approach for both web services and software. That's pretty much it. Which is why it isn't security at all. –  haylem Dec 15 '10 at 19:55
I think it's important to note that "security by obscurity" is usually a disparaging term: there is no such thing as " security by obscurity". That's not really what's being implied in the question, though... –  Dean Harding Dec 15 '10 at 23:56
"The safest secret is the one you don't reveal" –  JoelFan Dec 20 '10 at 18:50
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4 Answers

up vote 9 down vote accepted

Security by Obscurity is the process of making data so obscure it therefore becomes secure as no one can read/understand it.

Security by Obscurity means something else. It means that your security is based on the fact that you managed to hide the encryption algorithm from the prying eyes. If it becomes public, security is gone. You should not rely on keeping the algorithms hidden, but keep your specific encryption key secret.

Deleting the data is probably the best way to make it secure. Every encryption method is potentially vulnerable. If there is nothing to encrypt, then it's perfect. No data, no problem.

My question is what is the "term" for deleting data in order to make sure it is secure

There isn't one. But there is a strategy known as a secure wipe of the data. It means that not only you delete the files from the allocation table, but also wipe out the disk surface - by writing there zeros or something else, preferably several times over.

There is even a standard on how to do this properly for government organizations.

From the US Department of Defense, Standard DoD 5220.22-M / NISPOM 8-306:

US Department of Defense in the clearing and sanitizing standard DoD 5220.22-M recommends the approach "Overwrite all addressable locations with a character, its complement, then a random character and verify" (see table with comments) for clearing and sanitizing information on a writable media.

Feasibility of recovering overwritten data:

As of November 2007, the United States Department of Defense considers overwriting acceptable for clearing magnetic media within the same security area/zone, but not as a sanitization method. Only degaussing or physical destruction is acceptable for the latter.[4]

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Personally I'd use the phrase "shredding", though this would imply a secure delete where the data isn't just deleted but overwritten, potentially multiple times using a range of patterns to ensure it can't be recovered again.

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There are a variety of terms depending on what you're doing. In order of their chances of successful recovery these are:

1. Move to trash

You just move the file into a generic "recycle bin". You can fish it out later if you need to. Not secure at all. Perhaps this would be "security by obscurity" if you didn't know where the trashcan was.

2. Delete

This is usually synonymous with moving a file into a "marked for overwrite" state. The underlying operating system sets a flag against the file stating that it's OK to use the space occupied by this file. This overwrite may occur as a result of a system defrag operation, or maybe disk space is getting a bit tight. Often you can easily recover this type of operation using free online undelete tools.

3. Secure delete, wipe, shred

This involves marking the file as in the "delete" operation. In addition, a process immediately overwrites the data using a random set of data. Some implementations overwrite the data many times in many different ways to ensure that it cannot be recovered by conventional tools. Depending on the strength of randomness and the manner in which the write process interacts with the underlying medium (e.g. is it magnetic tape, magnetic disk, flash memory etc) it is possible to still retrieve data through forensic techniques. Perhaps using a super-conducting quantum interference device (SQUID) or somesuch.

4. Forensic delete

The final word in data destruction. All trace of the data is completely removed from the medium in a manner that renders it utterly impossible for it to be reconstructed through forensic techniques. This is normally physical destruction or putting the medium of data storage out of reach (dissolved in acid, buried in a nuclear reactor, blasted into space etc).

Hope it helps.


Undeleted my own answer in response to @Developer Art's comment. Somewhat apt given the context of the question, eh?

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It used to be "common knowledge" that formatting a drive made the data irretrievable... until Peter Norton accidentally discovered otherwise... and the rest is history –  JoelFan Dec 20 '10 at 19:00
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Maybe you're talking about a 'soft delete' where data are not deleted but just flagged as deleted so users can no longer access it?

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