At 10:20 AM 4/4/00 -0700, "Frates, Jarrod A." <[EMAIL PROTECTED]> wrote:
> > Camellia was designed to ensure security in usage for more than 20 years
>
>Based on Moore's Law, this means it will be secure on computers roughly
>10,000 times more powerful than today's systems. How likely is that?
Its not hard to imagine, if all we're talking about is brute force attacks.
Assume computers follow Moore's law for the next 20 years. The number of
doublings of computer speed would be 13.33 (=20/1.5). Lets round it up to
14 doublings to simplify. Then, the time it would take the computer
of the future to crack a 128-bit key, would be the same time it would take
a current computer to crack a key of 114 (=128-14) bits. To crack a 114-bit
key by brute force, 2E34 (=(2^114)/2) different keys would have to checked
on average. Suppose 100,000,000 PCs are used to crack the key. That would
take the same time it would take 1 PC to crack a key of 87.42
(=114-(Ln(100000000)/Ln(2))) bits. Lets round it down to 87-bits to
simplify. So an improbably massive effort (100,000,000 PCs), would
take the same time to crack a 114-bit key as a single PC would take to
crack an 87-bit key. 87-bits is impractical with current computers.
If a current PC could do 20,000,000 keys/sec, then it could do 6.3E14
(=20000000*365*24*60*60) keys in a year. Then it would on average
take 122E9 (=((2^87)/2)/6.3E14) years to crack the 87-bit key.
-- Tom
