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Task/RSA-code/Perl-6/rsa-code.pl6

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+constant $n = 9516311845790656153499716760847001433441357;
+constant $e = 65537;
+constant $d = 5617843187844953170308463622230283376298685;
+
+my $secret-message = "ROSETTA CODE";
+
+package Message {
+    my @alphabet = 'A' .. 'Z', ' ';
+    my $rad = +@alphabet;
+    my %code = @alphabet Z=> 0 .. *;
+    subset Text of Str where /^^ @alphabet+ $$/;
+    our sub encode(Text $t) {
+	[+] %code{$t.flip.comb} Z* (1, $rad, $rad*$rad ... *);
+    }
+    our sub decode(Int $n is copy) {
+	@alphabet[
+	    gather loop {
+		take $n % $rad;
+		last if $n < $rad;
+		$n div= $rad;
+	    }
+	].join.flip;
+    }
+}
+
+use Test;
+plan 1;
+
+say "Secret message is $secret-message";
+say "Secret message in integer form is $_" given
+    my $numeric-message = Message::encode $secret-message;
+say "After exponentiation with public exponent we get: $_" given
+    my $numeric-cipher = expmod $numeric-message, $e, $n;
+say "This turns into the string $_" given
+    my $text-cipher = Message::decode $numeric-cipher;
+
+say "If we re-encode it in integer form we get $_" given
+    my $numeric-cipher2 = Message::encode $text-cipher;
+say "After exponentiation with SECRET exponent we get: $_" given
+    my $numeric-message2 = expmod $numeric-cipher2, $d, $n;
+say "This turns into the string $_" given
+    my $secret-message2 = Message::decode $numeric-message2;
+
+is $secret-message, $secret-message2, "the message has been correctly decrypted";