If this option is used, DSA rather than DH parameters are
read or created; they are converted to DH format. Otherwise, "strong"
primes (such that (p-1)/2 is also prime) will be used for DH parameter generation.
DH parameter generation with the -dsaparam option is much
faster, and the recommended exponent length is shorter, which makes
DH key exchange more efficient. Beware that with such DSA-style
DH parameters, a fresh DH key should be created for each use to
avoid small-subgroup attacks that may be possible otherwise.