.Dd April 14, 1997
.Dt BIGPRIME 1
.Os NetBSD 1.2BETA
.Sh NAME
.Nm bigprime
.Nd big prime generator
.Sh SYNOPSIS
.Nm
.Op Fl i
.Op Fl I
.Op Fl x
.Op Fl b Ns Ar N
.Op Fl t Ns Ar N
.Op Fl v Ns Op Cm v...
.Ar nbits
.Sh DESCRIPTION
.Nm
generates a prime
.Ar nbits
bits long, printing it to stdout in decimal.  By default, it gets the
basic randomness it needs by running various system utilities, such as
.Xr ps 1
and
.Xr netstat 1 .
If
.Fl i
is given, it also reads its standard input to EOF and uses that as
additional randomness.  If
.Fl I
is given, standard input is read and the other sources are ignored.
This is emphatically not recommended; the option exists for people who
have a relatively high-bandwidth source of strong random bits and don't
want to (or can't) wait for the normal randomness-gathering process.
.Pp
Of course, for reasonably large values of
.Ar nbits ,
it is not feasible to fully test the generated number for primality.  A
large number of small primes are tested against; once those are passed,
a test based on Fermat's Little Theorem is done, and if that too is
passed, several iterations of a probabilistic primality test are done,
each iteration having probability at least 3/4 of detecting a nonprime.
By default, 32 such iterations are done, meaning the probability that
the number output is not prime is no greater than one in 2^64;
additional paranoia may be added at the cost of running time (or faster
running time may be obtained at the cost of lessened checking) by
specifying
.Fl t ,
which takes an argument giving the number of iterations of the
probabilistic test to do.
.Pp
.Fl v
causes
.Nm
to be chatty on stderr, printing various progress messages as it does
its thing.  Specifying
.Fl v
multiple times increases the level of chattiness.
.Pp
By default, the generated number is output in decimal.  Specifying
.Fl b Ns Ar N
produces output in base
.Ar N
instead;
.Fl x
is an abbreviation for
.Fl b Ns Ar 16 .
.Sh BUGS
Feeding large amounts of data to the
.Fl i
option tends to be computationally expensive (but for some applications
may be worth it).
.Sh AUTHOR
der Mouse,
.Aq mouse@rodents.montreal.qc.ca .