> Wow, Linus raises an entirely different issue which is that the PDF-based attack can't and won't work on git at all. Due to length prefixing it is extremely difficult to insert some nonsense into the middle of a git object which is how this attack works on PDFs.
Please note that the shattered-{1,2}.pdf files both have exactly the same length. And even with cleartext it is easy to pad passages so they contain the same amount of bytes. See how the quoted paragraph above has exactly the same number of characters as this one.
>>> len('''> Wow, Linus raises an entirely different issue which is that the PDF-based attack can't and won't work on git at all. Due to length prefixing it is extremely difficult to insert some nonsense into the middle of a git object which is how this attack works on PDFs.''')
264
>>> len('''Please note that the shattered-{1,2}.pdf files both have exactly the same length. And even with cleartext it is easy to pad passages so they contain the same amount of bytes. See how the quoted paragraph above has exactly the same number of characters as this one.''')
264
Indeed, they probably have to have the same length since the length is inserted into the final block as part of SHA-1 hashing and every block after the collision must be the same. I don't think it's even possible to create a MD5 collision between two documents of different length yet.
Please note that the shattered-{1,2}.pdf files both have exactly the same length. And even with cleartext it is easy to pad passages so they contain the same amount of bytes. See how the quoted paragraph above has exactly the same number of characters as this one.