Re: A factoring algorithm

hart_wb@yahoo.com wrote:
> b needs to be the same, the others may differ, but you don't want the
> n's to vary by too much unless you have a lot of time on your hands,
> though variations of the algorithm get around this to a certain extent.
> I haven't worried too much about that though, since it is my impression
> that RSA moduli are often picked with the primes within 3 or 4 digits
> of each other in length.

FYI, typically 2-prime RSA moduli have factors of the same bit
length. (I base this on having seen a lot of implementations; I
don't actually know everyone's private keys.)

A popular method to create 2n-bit RSA keys is to pick both primes
(randomly, independently) in the range:

    [ceiling(2**(n-1) * sqrt(2)), 2**n)

There's various old advice to pick primes a few digits apart,
construct them non-randomly, or filter out primes with certain
properties. The reasons for such advice are now refuted.

-- 
--Bryan