Create chinese_cipher.pl

cryptography/chinese_cipher/perl/chinese_cipher.pl

@@ -0,0 +1,97 @@
+#!/usr/bin/env perl
+
+sub encrypt
+{
+  my $data = shift;
+
+  my $encoded_data = '';
+
+  my $length = length $data;
+  my $sqrt = int(sqrt($length));
+  $sqrt++ unless (($sqrt * $sqrt) >= $length);
+  my @unencoded = split(//, $data);
+  my @message;
+  my $minside = $sqrt;
+  if (($sqrt * $sqrt) > $length) {
+    while (($minside * $sqrt) > $length) { $minside--;};
+    $minside++; # ensure square can hold the string
+  }
+
+  for (my $j = 0; $j < $sqrt; $j++) {
+    if ((($sqrt - $j)%2) == 0) {
+      for (my $i = $minside-1; $i >= 0; $i--) {
+        my $char = shift @unencoded;
+        $message[$i][$j] = $char;
+      }
+    } else {
+      for (my $i = 0; $i < $minside; $i++) {
+        my $char = shift @unencoded;
+        $message[$i][$j] = $char;
+      }
+    }
+  }
+
+  for (my $i = 0; $i < $minside; $i++) {
+    for (my $j = 0; $j < $sqrt; $j++) {
+      if (defined $message[$i][$j]) {
+        $encoded_data .= $message[$i][$j];
+      } else {
+        $encoded_data .= " ";
+      }
+    }
+  }
+
+  return $encoded_data;
+}
+
+sub decrypt
+{
+  my $data = shift;
+
+  my @chars = split(//, $data);
+  my $length = length $data;
+  my $sqrt = int(sqrt($length));
+  if (($sqrt * $sqrt) < $length) {
+    $sqrt++;
+  }
+  my $minside = $sqrt;
+  if (($sqrt * $sqrt) > $length) {
+    while (($minside * $sqrt) > $length) { $minside--;};
+    $minside++; # ensure square can hold the string
+  }
+
+  my @message;
+  for (my $i = 0; $i < $minside; $i++) {
+    for (my $j = 0; $j < $sqrt; $j++) {
+      my $char = shift @chars;
+      $message[$i][$j] = $char;
+    }
+  }
+
+  my $decoded_data = '';
+  for (my $j = 0; $j < $sqrt; $j++) {
+    if ((($sqrt - $j)%2) == 0) {
+      for (my $i = $minside-1; $i >= 0; $i--) {
+        $decoded_data .= $message[$i][$j];
+      }
+    } else {
+      for (my $i = 0; $i < $minside; $i++) {
+        $decoded_data .= $message[$i][$j];
+      }
+    }
+  }
+
+  #trim decoded_data
+  $decoded_data =~ s/\s+$//;
+
+  return $decoded_data;
+}
+
+sub test {
+  my $text = shift;
+  my $encrypted = encrypt($text);
+  my $decrypted = decrypt($encrypted);
+  return $decrypted eq $text;
+}
+
+print "Got expected message\n" if test('This is a test');