#!/usr/bin/perl

use CGI ':standard';
use Digest::SHA qw(sha512);
use Crypt::OpenSSL::Random;
use Crypt::OpenSSL::RSA;


$passphrase = param('genpass');
$prngdata = "";
print "Content-Type: text/html\n\n";

if ($passphrase) {
  Crypt::OpenSSL::Random::random_seed(&genrsarandom(1024));
  Crypt::OpenSSL::RSA->import_random_seed();

  $rsa = Crypt::OpenSSL::RSA->generate_key(1024);


print "PRNG data length: ". length($prngdata)."<br>";
print "PRNG data in hex: " . uc(unpack("H*", $prngdata)) . "<br><br>";

$pubkey = $rsa->get_public_key_string();
$privkey = $rsa->get_private_key_string();
$pubkey =~ s/\n/<br>/sgi;
$privkey =~ s/\n/<br>/sgi;
print "Public key: <br>" . $pubkey . "<br><br>";
print "Private key: <br>" . $privkey;

}
else
{
print "<form action=\"RSAgen.cgi\">PassPhrase: <input type=\"text\" name=\"genpass\"><input type=\"submit\" value=\"genrsa\"></form>";
}

####################################################
# CSPRNG BASED ON A PASSWORD
# RETURNS SAME RANDOM DATA UPON SUPPLYING
# THE SAME PASSWORD
####################################################

sub genrsarandom() {
$bytes = $_[0];
$randomdata = "";
$numberofrounds = int($bytes / 64) + 1;

for ($i = 0; $i < $numberofrounds; $i++) {
$randomdata = $randomdata . sha512($passphrase . sha512($i.$i));
}

$randomdata = substr($randomdata, 0, $bytes);
$prngdata = $randomdata;
return $randomdata;
}