[Cryptography] Collisions w/SHA-1 ~$100,000 TODAY

[Scott Elcomb]

On Sat, Oct 10, 2015 at 11:40 AM, ianG <iang at iang.org> wrote:
> Can anyone provide a pointy-eared boss description of what a *freestart*
> collision is?

The closest I've found is "A freestart collision is a collision where
the attacker can choose the initialisation vector."


Source: <http://crypto.stackexchange.com/a/29696>

In the Damgard-Merkle construction for hash functions the compression
function takes as input:

* a message block and
* a chaining value.

For the very first block there is not previous "chaining value".
Instead a particular value, called an initialisation vector (IV) is
given.

A freestart collision is a collision where the attacker can choose the IV.


-- 
  Scott Elcomb         @psema4
     http://www.pirateparty.ca/