rsa.p6

sub random-prime(:$digits) {
  repeat { $_ = (10**$digits .. (10**($digits+1))).pick } until .is-prime;
  return $_;
}

sub encrypt(:$message, :$key) {
  return expmod($message,$key[0],$key[1])
}

sub decrypt(:$message, :$key) {
  return expmod($message,$key[0],$key[1])
}

my $q = random-prime(:110digits);
my $p = random-prime(:110digits);
my $pq = $p * $q;
my $phi = ($p-1) * ($q-1);
my $k;
repeat {
  $k = (1..$pq).pick;
} until $k gcd $phi == 1;

my $inverse = expmod($k, -1, $phi);
my $public = [ $k , $pq ];
my $private =[ $inverse, $pq ];

use Test;

for 1..100 {
  my $plain = (1..$pq).pick;
  my $encrypted = encrypt(message => $plain, key => $public);
  my $decrypted = decrypt(message => $encrypted, key => $private);
  ok $decrypted==$plain, "decrypted message";
}

done-testing;