Concatenating files can generate same hash?

[richardhuaaa]

As far as I understand, this works by concatenating all of the files together and then hashing the result. Does this mean that we can get the same hash when hashing this:

File 1: 00 01 02
File 2: 03 04 05

As well as this?

File 1: 00 01 02 03
File 2: 04 05

[mac-]

That's true, thanks for uncovering this issue. I'll get this fixed soon.

[richardhuaaa]

Oh, just another thing to note, I'm not sure how important this is to you, but this hashing algorithm also doesn't seem to factor in the names of the files. So if a file got renamed from a.js to aa.js, the hash would still come out the same.

[monteiz]

To solve both the issues at once, it would be enough to concatenate the full path of the file to the file data, and then hash.

I would create a PR, but I suppose this project is abandoned.

[andersk]

To solve both the issues at once, it would be enough to concatenate the full path of the file to the file data, and then hash.

@monteiz No, because then you’d still get collisions like this:

• file file1.txt with contents _foo_file2.txt_bar_ and file file2.txt with contents _baz_
• file file1.txt with contents _foo_ and file file2.txt with contents _bar_file2.txt_baz_

which would both be smashed into file1.txt_foo_file2.txt_bar_file2.txt_baz_ and hashed to the same result.

To solve these issues, you need to encode the filenames and corresponding data into a stream from which they could be unambiguously recovered, for example, files.map((file) => file.name.length + " " + file.name + file.data.length + " " + file.data).join("").

[monteiz]

@andersk good observation