[tahoe-dev] SHA-1 broken!

[Christian Rechberger]

> On Sat, May 2, 2009 at 12:33 PM, Perry E. Metzger <perry at piermont.com> wrote:
>
>> As just one obvious example of a realistic threat, consider that there
>> are CAs that will happily sell you certificates that use SHA-1.
>>
>> Various clever forgery attacks have been used against certs that use
>> MD5, see:
>>
>> http://www.win.tue.nl/hashclash/rogue-ca/
>>
>> Those attacks can now be extended to SHA-1 pretty easily. It might
>> require a bit of compute infrastructure -- say a lot of FPGAs and a
>> bunch of cleverness -- to turn out certs quickly, but it can be
>> done. Given that there are lots of high value certs out there of this
>> form, this is rather dangerous.
>
> Off-the-shelf FPGA-based device that breaks DES by brute force in
> about a week, costs 9,000 euros: http://www.copacobana.org/
> These are commercially available and programmable. Setting a
> few of them up to break SHA-1 certainly would not be trivial,
> but it looks feasible.

The design of DES facilitates this kind of throughput/cost gains on FPGAs.

Remember that the MD4 family (incl. SHA-1) was designed to be  
efficient on 32-bit CPUs. For these hash functions, it is much harder  
to get a throughput/cost gain on FPGAs compared to off-the-shelf CPUs.  
At least, this was my conclusion when I quickly looked into this a few  
years ago.

Best,
  Christian

-- 
Christian Rechberger, Graz University of Technology, Austria

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