#!/usr/bin/perl
use CGI qw(param);
# Compute RSA encryption: m^a (mod n)
print "Content-type: text/html\n\n";
print "Output
\n";
my $m = param("inputm");
my $a = param("inputa");
my $n = param("inputn");
$m=int($m);
$a=int($a);
$n=int($n);
$errorm=0;
$errora=0;
$errorn=0;
if($m<=0){$errorm=1;
print "Your value of m must be an integer bigger than 0.
\n";}
if($a<=0){$errora=1;
print "Your value of a must be an integer bigger than 0.
\n";}
if($n<=0){$errorn=1;
print "Your value of n must be an integer bigger than 0.
\n";}
if($m>10000000){$errorm=2;
print "Your value of m must be an integer less than 10,000,000.
\n";}
if($a>10000000){$errora=2;
print "Your value of a must be an integer less than 10,000,000.
\n";}
if($n>10000000){$errorn=2;
print "Your value of n must be an integer less than 10,000,000.
\n";}
if($errorm+$errora+$errorn>0){print "Please try again.
\n";} else
{$gcf=EuclidAlg($m,$n);
print "Note: gcf($m,$n)=$gcf.
\n";
$i=$a;
$p=1;
while($i>0){
$p=($p*$m)%$n;
$i=$i-1;
}
print "Here is your answer: $m$a = $p (mod $n)\n\n\n\n\n";
}
print "\n";
sub EuclidAlg { # This subroutine does Euclid's Algorithm and returns gcf(a, b)
my($a,$b) = @_;
my($r);
$r = $a%$b;
while($r>0){
$a=$b;
$b=$r;
$r=$a%$b;
# print "$a, $b, $r\n";
}
return ($b);}