3 ms·
As other people explained, and just to summarize, this service is a way of reusing Google's specific collision (as a prefix to new collisions), and isn't a way
by schoen 10y ago
As other people explained, and just to summarize, this service is a way of reusing Google's specific collision (as a prefix to new collisions), and isn't a way of making arbitrary colliding files or file formats. You can't, for example, use this to make something other than PDFs that collide; for that, you'll have to redo a computation on the scale of Google's!
- dheera 10y agoWhy wouldn't you be able to? Most file formats have ways of including comment data, including JPEG, GIF, HTML, C code, and most others. You could potentially create a piece of noble C code and a piece of malicious C code that collide. (However, creating a piece of malicious code that matches an existing codebase that doesn't contain a comment would be hard, if I understand correctly.)
- aidenn0 10y agoThis reuses the prefix that Google calculated, which is a PDF header. Therefore you can only generate PDFs with this technique. If you want to dedicate a few hundred GPU-years to it, you could generate similar colliding prefixes for other formats by doing what Google did.
- dheera 10y agoAh, I see, thanks.
- orblivion 10y agoI thought I heard that some file formats have "headers" that go at the end of the file. I think a demo of this was a file that was both a zip and a PNG or something. If I remembered right, you should be able to make a similar hack here.
- schoen 10y agoIf the only headers are at the end, then yes, that's a really neat idea. I'm not sure of the constraints for zip files. Maybe it would be interesting to brainstorm with some people with a lot of file format knowledge to find additional such formats. But if the formats have any constraints at all on the first few hundred bytes, those generally won't be satisfied by the prefix here.