hi, I get the point.Thanx for all the replies.
regards Data. --- Joseph Ashwood <[EMAIL PROTECTED]> wrote: > > ----- Original Message ----- > From: "gfgs pedo" <[EMAIL PROTECTED]> > > > > > Oh surely you can do better than that - making > it > > > hard to guess the seed > > > > is also clearly a desirable property (and one > that > > > the square root "rng" > > > > does not have). > > U can choose any arbitrary seed(greater than 100 > bits > > as he (i forgot who) mentioned earlier.Then > subject it > > to the Rabin-Miller test. > > Since the seed value is a very large number,it > would > > be impossible to determine the actual value.The > > chances the intruder find the correct seed or the > > prime number hence generated is practically verly > low. > > You act like the only possible way to figure it out > is to guess the initial > seed. The truth is that the number used leaves a > substantial amount of > residue in it's square root, and there are various > rules that can be applied > to square roots as well. Since with high likelihood > you will have a lot of > small factors but few large ones, it's a reasonable > beginning to simply > store the roots of the first many primes, this gives > you a strong network to > work from when looking for those leftover > signatures. With decent likelihood > the first 2^32 primes would be sufficient for this > when you choose 100 bit > numbers, and this attack will be much faster than > brute force. So while you > have defeated brute force (no surprise there, brute > force is easy to defeat) > you haven't developed a strong enough generation > sequence to really get much > of anywhere. > > > > Of course, finding the square root of a 100 > digit > > > number to a > > > precision of hundreds of decimal places is a lot > of > > > computational > > > effort for no good reason. > > Yes the effort is going to be large but why no > good > > reason? > > Because it's a broken pRNG, that is extremely > expensive to run. If you want > a fast pRNG you look to ciphers in CTR mode, or > stream ciphers, if you want > one that's provably good you go to BBS (which is > probably faster than your > algorithm anyway). So there's no good reason to > implement such an algorithm. > > > > BTW, the original poster seemed to be under the > > > delusion that > > > a number had to be prime in order for its square > to > > > be irrational, > > > but every integer that is not a perfect square > has > > > an irrational > > > square root (if A and B are mutually prime, > A^2/B^2 > > > can't be > > > simplified). > > > > Nope ,I'm under no such delusion :) > > Just the delusion that your algorithm was good. > Joe > __________________________________________________ Do You Yahoo!? Yahoo! Games - play chess, backgammon, pool and more http://games.yahoo.com/
