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File already exists

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I dont know if it is a bug or missing Knowledge on my Side.
I try to upload a Scan but i get the error...

The following errors occured:

file: This file already exists.

Is it a bug? did i get a restriction without knowing? if i click on " already exists" it links to a deletion mail from Vkun
Kikou Shoujo wa Kizutsukanai by Vkun
Kikou Shoujo wa Kizutsukanai by Vkun

dont know if the System can automaticly see Scans i try to upload and know that they were deleted once or not in the past from other Members ( I doubt that MT got a AI like that) so i would like to know what iam dealling with, since i dont got any other scan right now to upload i cant try it out with others.

Just seen the that its the same scan i try to upload in the Thumbmail of the Post here

MisaSasekage

Moderator

MisaSasekage

War Queen

If it redirected you to a deletion, that means it was in the gallery & previously deleted. Sometimes the system catches items that were in the gallery & deleted and therefore stops you from posting them again.

It's not really a bug or anything like that.

Thank you for the help Misa, it makes sense! didnt knew the System can do it so i wonder if its because of a AI or not cause i added a -1 at the end of the original file name so im interested in knowing how the system can see it exept the AI i programmed to check multiple Parameters.
Anyway it helped out thanks again

MisaSasekage

Moderator

MisaSasekage

War Queen

No problem at all, you're very welcome Shimazaki. Glad I could help :)

It doesn't always work, but I'm guessing the system can sometimes recognize/"remember" the image even if it's been previously deleted.

UsagixKitsune

UsagixKitsune

nsɐƃıxʞıʇsnuǝ

Quote by Shimazakidont know if the System can automaticly see Scans i try to upload and know that they were deleted once or not in the past from other Members ( I doubt that MT got a AI like that) so i would like to know what iam dealling with

If you have ever been to a site like Danbooru you might have noticed the weird file names which look like this "13167de4acac50e12872eab5fbbc7bfc.jpg".

The long 32 digit number (yes A-F are numbers) is called the checksum of the file. This number is calculated based on the content of the file and is unique to that file. This is how websites can keep track of which files have already been uploaded and deleted without keeping a copy of every file and doing pixel by pixel comparisons of the images. It is also the starting point for forensic investigators looking for known illegal files or malware on a computer.

A major weakness of traditional checksum algorithms such as md5 (what Danbooru and friends use) is that the slightest change in the file causes a completely different checksum to be generated. Notice I said file not image. Simply appending a null byte on the end of the file will allow you to re-upload a banned file on most websites and in the case of images at least it will not change the meaning of the content (you won't see anything different about the picture).

Quote by shell$ md5sum a.png
703b52ddba099df2806406309d931184 a.png
$ truncate -s +1 a.png
$ md5sum a.png
bd5d2a80efe4c31bff5e6ba507a72606 a.png

There is such a thing as fuzzy hashing algorithms which produce output more closely matching patterns inside files so a small change like appending a null byte will return a very similar checksum to the original which is much better at detecting files with only slight variations. In reality most websites stick with algorithms like md5 because they are much faster and that makes it cheaper to run the servers.

An interesting side note is that checksums also have an application in the security space since they can be used to help prove that a file came from a trusted source and has not been tampered with since it should be impossible to generate 2 files with the same checksums. You may remember the Flame malware that hit the news a few years ago. Part of the reason this was such a big deal was because they used an md5 collision to hijack Windows update and infect victims. Before that point md5 collisions were only theoretically possible so it was a pretty badass attack. Don't worry, Microsoft have obviously upgraded the Windows update mechanism since then.

im sure i get the important parts XD thanks, it explained a lot to me

UsagixKitsune

UsagixKitsune

nsɐƃıxʞıʇsnuǝ

Hopefully I dropped enough keywords you can use to do extra research if you'd like to find out more.

Great scan by the way ^_^V

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