3 ms·
the two PDFs used the same (colliding) prefix and included both files you supplied. once you've reached a hash collision, any number of identical blocks after t
by f2f 10y ago
the two PDFs used the same (colliding) prefix and included both files you supplied. once you've reached a hash collision, any number of identical blocks after that would hash the same.
if you want a proof, submit a different image: the hashes will be identical, but different from your first attempt.
- jeffdavis 10y agoCan you explain the difference between a collision attack and a preimage attack? How can you get two PDFs with arbitrary contents having the same SHA1 without a preimage attack?
- jobigoud 10y agoThe pdfs don't have arbitrary content, they contain very specific headers (crafted by Google research), in one file the header selects one image, in the other it selects the other. These two headers are SHA1 colliding and the remainder of the files are identical.
- jeffdavis 10y agoOh, that makes sense. Thank you!