This method generates the DSS
p,
q, and
g parameters only when
L (the modulus length)
is not one of the following:
512,
768 and
1024. For those values of
L, this implementation
uses pre-computed values of
p,
q, and
g given in the document
CryptoSpec included in the
security guide documentation of the standard JDK distribution.
The DSS requires two primes ,
p and
q,
satisfying the following three conditions:
2159 < q < 21602L-1 < p < 2L for a
specified L, where L = 512 + 64j for some
0 <= j <= 8- q divides p - 1.
The algorithm used to find these primes is as described in FIPS-186,
section 2.2: GENERATION OF PRIMES. This prime generation scheme starts by
using the
Sha160 and a user supplied
SEED
to construct a prime,
q, in the range 2
159 < q
< 2
160. Once this is accomplished, the same
SEED
value is used to construct an
X in the range
2L-1
< X < 2L. The prime, p, is then
formed by rounding
X to a number congruent to
1 mod
2q. In this implementation we use the same
SEED value given
in FIPS-186, Appendix 5.