Question

I need to delete my input file securely once I have finished with it, at the moment I’m overwriting all the data with zero, this is messy as my temp folder becomes full of old files also the name of the files is a security issue.

Rather than just moving them to the recycle bin I would like them to skip it and just disappear, this is in conjunction with being wiped byte wise as data recovery software can recover items from beyond the recycle bin. As the name is also important I need to rename them before I delete them.

Answer 1

This is a progressive problem. What is ‘secure’ for one application is insecure for another. If security is really important and you find yourself asking these kinds of questions on Stack Overflow, then most likely need to contract with an external security consultant. Examples of really important include financial information, medical records, or anything else where there is a law or contract requiring the securing of the data. I don’t say this to be mean or imply that you are incapable of solving the problem, but to point out that this is a rather complex and evolving problem.

Basically to accomplish what you want to accomplish:

1. Once your code you wrote finishes then change the file size to empty – this makes recovery more difficult because the original file size is lost.
2. Then rename the file (RenameFile)to a different name.
3. Finally delete the file using DeleteFile, which does not move the file to the recycle bin.

Make sure you maintain an exclusive handle on the files the whole time they are on the disk too, or they can just be copied before they are deleted.

As I said, this is a progressive problem. This is a really basic solution, and is subject to a number of vulnerabilities. So depending on the level of security needed you might consider never letting the file be written to disk, or using multiple pass overwrites. If security is really important, then actually burning the hard drive platter at a high temperature, and then smashing it is the only way to be sure.

Edit: It appears you removed your code sample.