openssl/doc/apps/genrsa.pod

=pod

=head1 NAME

genrsa - generate an RSA private key

=head1 SYNOPSIS

B<openssl> B<genrsa>
[B<-out filename>]
[B<-passout password>]
[B<-envpassout var>]
[B<-des>]
[B<-des3>]
[B<-idea>]
[B<-f4>]
[B<-3>]
[B<-rand file(s)>]
[B<numbits>]

=head1 DESCRIPTION

The B<genrsa> command generates an RSA private key.

=head1 OPTIONS

=over 4

=item B<-out filename>

the output filename. If this argument is not specified then standard output is
used.  

=item B<-passout password>

the output file password. Since certain utilities like "ps" make the command line
visible this option should be used with caution.

=item B<-envpassout var>

read the output file password from the environment variable B<var>.

=item B<-des|-des3|-idea>

These options encrypt the private key with the DES, triple DES, or the 
IDEA ciphers respectively before outputting it. If none of these options is
specified no encryption is used. If encryption is used a pass phrase is prompted
for if it is not supplied via the B<-passout> or B<-envpassout> arguments.

=item B<-F4|-3>

the public exponent to use, either 65537 or 3. The default is 65537.

=item B<-rand file(s)>

a file or files containing random data used to seed the random number
generator. Multiple files can be specified separated by a OS-dependent
character.  For MS-Windows, the separator is B<;>.  For OpenVMS, it's
B<,>.  For all others, it's B<:>.

=item B<numbits>

the size of the private key to generate in bits. This must be the last option
specified. The default is 512.

=back

=head1 NOTES

RSA private key generation essentially involves the generation of two prime
numbers. When generating a private key various symbols will be output to
indicate the progress of the generation. A B<.> represents each number tested.
A B<+> means a number has passed a single primality test. A newline means that
the number has passed all the prime tests (currently set to 5 single tests).

Because key generation is a random process the time taken to generate a key
may vary somewhat.

=head1 BUGS

A quirk of the prime generation algorithm is that it cannot generate small
primes. Therefore the number of bits should not be less that 64. For typical
private keys this will not matter because for security reasons they will
be much larger (typically 1024 bits).

=head1 SEE ALSO

L<gendsa(1)|gendsa(1)>