Timeline for Is calculating a hash code for a large file in parallel less secure than doing it sequentially?
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| Aug 11, 2011 at 13:57 | comment | added | poncho | Actually, it is clear that method 2 is at least as strong as method 1, in this strong sense: if you have an algorithm that finds a collision in method 2 with probability p and computational effort N, then you also have a method to find a collision in method 1 that works with probability p and computational effort N+\epsilon (where \epsilon counts for the effort of examining the subhashes, and finding what collided internally) | |
| Aug 11, 2011 at 2:49 | comment | added | Michael Goldshteyn | The thing is that with Method 2 we can have a collision in the final hash, without having collisions at the intermediate hashes. Also, if we break a large file into 1 MB chunks, we have the possibility of a collision on one of the chunks, but which does not lead to a collision of the final hash. This is why it's not at all clear if any hash strength is lost with Method 2. | |
| Aug 10, 2011 at 20:30 | history | answered | poncho | CC BY-SA 3.0 |