3 ms·
The interesting aspect that a lot of people are overlooking is that, for a theoretical attack within certain timeframes, this difference can be make-it or break
by omeid2 8y ago
The interesting aspect that a lot of people are overlooking is that, for a theoretical attack within certain timeframes, this difference can be make-it or break it!
Imagine a collision attack that takes about a 1 year with 64bit serial numbers, so with 63bit serial number it should take about half, at 6 months.
The average certificate is issued for about 1 year, so being able to mount a collision attack that took 1 year in 6 months can make the difference from generally-not-useful to very practical and dangerous.
- p1mrx 8y agoWhy do you assume that an attack would take 1 year, and not (e.g.) a billion years? A factor of two is only interesting if the number you're dividing was interesting in the first place.
- deleted 8y ago[deleted]
- omeid2 8y agoimagine is hardly assuming. But it doesn't have to be exactly 1 year, any attack that takes longer but less than 2x average certificate lifetime with 64bit serial numbers (useless) becomes practical on 63bit serial numbers (useful, for a strange meaning of useful).
- fwip 8y agoSuch an attack doesn't exist. Any such attack would also become feasible with twice the budget.
- omeid2 8y ago> Such an attack doesn't exist. As far as we know. > Any such attack would also become feasible with twice the budget. Assuming that the attack yields to parallel computing and scales linearly with more cpu/cores, because linear programming is bound to current compute capabilities and then theoretical limits like Bremermann's limit and Margolus–Levitin theorem.
- underwater 8y agoIn your scenario half of the 64 bit certificates could be brute forced in 6 months anyway.