[BitTorrent] SHA-0 Broken, MD5 Rumored Broken

Marcel Popescu mdpopescu at yahoo.com
Sat Aug 21 10:57:46 EDT 2004


From: "Elliott Mitchell" <ehem at m5p.com>

> Interestingly if there is a break and it only affects the strongly
> collision free property of SHA-1, then you could make breakable files.
> Use slack (comments fields, any chunks that will be thrown out) in your
> file(s) to make a file with matching hashes. Once past a certain date
> you can thoroughly kill the file.

The only problem with SHA-1 is theoretical so far: you can generate 2^80
collisions with "only" 80 * 2^80 work, instead of the theoretical 2^80 *
2^80. That's bad (and it will, according to the guys on the cypherpunks
groups, lead to new research in the field), but only bad in the sense of
"the Sun might burn out in only 4 billion years, instead of 5". No need to
worry about it.

What HAS been broken are MD5 (completely) and SHA-0 (apparently here only a
collision was found, but the consensus is that the algorithm is doomed
anyway). However, since it's been obsolete for a lot of years, that doesn't
really matter.

Marcel




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