SHA-1 Broken

Nanolith writes "From Bruce Schneier's weblog: 'SHA-1 has been broken. Not a reduced-round version. Not a simplified version. The real thing. The research team of Xiaoyun Wang, Yiqun Lisa Yin, and Hongbo Yu (mostly from Shandong University in China) have been quietly circulating a paper announcing their results...'" Note, though, that Schneier also writes "The paper isn't generally available yet. At this point I can't tell if the attack is real, but the paper looks good and this is a reputable research team."

Comments

Re:Info on what exactly SHA-1 is ...

[Anonymous Coward]

Any encryption scheme that lasts about 10 years has given a pretty good service I would think.

SHA-1 is not an encryption scheme, it's a cryptographic one-way hash function.

There's a significant difference.

Re:So what's the big deal for the rest of us?

[iabervon]

It is still probably difficult (hard to say without looking at the paper) for someone to find a different document with the same hash as a document you create, but it's now not all that hard to find a pair of documents with the same hash. Someone could give you a document to sign, and get your signature on a different document. Also, IIRC for previous work by this group, the attack applies to chosen pairs of documents with sufficient "random" padding; you can search for a padding for each to generate a hash collision.

Essentially, don't sign anything that someone else has given you without changing it in some way, or your signature might also apply to some other document they have chosen.

Re:Cryptographic break =/= practical break

[Deliveranc3]

Guess who wants to send meaningless data... bittorrent relies on SHA-1 which is I imagine what the moderator was most interested in.

I might be paranoid but it wouldn't be inconceivably difficult for **AA to upload single blocks of corrupted data and destroy every torrent as it streams, they certainly have the resources.