- even though 128 bit encryption is supposed to be nearly impossible to crack....
Wait a second now... Ive had at least 2 generations of computers, with a third now available, P3\Athlon, AMD 64\P4, and the new Pentium Core extrem/Core duo.
So, when running a P3, sure i might say sure, nearly impossible to crack. Then we have AMD 64\P4 with Dual Core... that would cut the time a bit to crack 128 bit. Then the relases of Core Duo= to to up grade if you ask me.
We went from 32 bit cunks of data to 64 bit, if you care for XP 64\Linux\Apple(eek!)
So..... Me thinks we need at least 256 bit encryption to be able to say "nearly impossibel to crack" again.
But i could be full of it.
While I would recommend 256bits just to be done with it, 128bits is hardly insecure (assuming the encryption algorithm is strong).
Using a single Core 2 Duo processor, and assuming a full key comparison per clock cycle (that is impossible - it is usually more like 10-20 cycles per key check), it would take (on average, of course) more years to calculate the answer than the age of the universe. By many magnitudes.
To prove the math:
((2^128)/2)/((2.93x10^9)*2) = 2.9x10^28 seconds, or 92,000,000,000,000,000,000 years.
Even if there was a petaflop computer and, once again, it did 1 key check per cycle (which is impossible), then it would still take 540,000,000,000,000 years.
Once again, this is if the encryption method is sound: recent cryptographical work has shown certain methods to reduce the key search on certain modern encryption schemes by as much as 10 magnitudes, which means that it is becoming possible to, if given unlimited resources, crack a 128 bit key in only a few hundred years using current technology. There are also other methods to search for a key, such as sieving or factorization, but they tend to be even more impractical than brute forcing the key if the encryption method is strong.
In other words, it doesn't really matter how much you use. 128 bits is fine, but it isn't like going to 256 bits will really slow down your encryption much, so go ahead and use it if it gives you warm fuzzies.