4 ms·
This is almost certainly true in practice, but it's a big risk, compared to the risk tolerance that we usually engineer into crypto. For comparison, suppose som
by oconnor663 7y ago
This is almost certainly true in practice, but it's a big risk, compared to the risk tolerance that we usually engineer into crypto. For comparison, suppose someone was suggesting: "Why not use 80-bit keys instead of 128-bit keys? No one in the real world can brute force 80 bits, and we'll save on storage." Yes, that's true, but it's taking a relatively large risk for relatively little benefit. Hardware will get faster over time, and an extremely high value target might justify an extremely expensive attack, etc etc. We prefer 128-bit keys because then we don't even have to consider those questions. I think timing attacks are similar: Yes they're very difficult in practice, but they raise questions that we'd rather not have to think about. (And which, realistically, no one will ever revisit in the future, as hardware evolves and new APIs are exposed.)
- necovek 7y agoI always imagined key size to relate to computation cost and not storage — what algorithm are you referring to?
- joshuaissac 7y agoThe point is that you need more bits to store a longer key, but the storage space saved is very little in this case compared to how much easier it is to crack.
- necovek 7y agoSure, but a difference of 0.1% of storage to go from 80-bit key to 1024-bit key for 1 Megabit of data (that's 118 bytes out of 128KiB), or 0,00001% for 1Gbit (128MiB) seems not worth raising as a concern. (I've chosen example numbers just to make calculation trivial) So I can't ever imagine storage size being the driver for choosing the key size, though from the other threads, it seems that there are algorithms that do have a storage overhead that might be related to key sizes.