Merge pull request ZoranPandovski#106 from nawglan/nawglan-chinese-ci…

…pher

Nawglan chinese cipher

cryptography/chinese_cipher/README.md

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+from: https://en.wikipedia.org/wiki/Classical_cipher#Transposition_ciphers
+
+In the Chinese cipher's method of transposing, the letters of the message are written from right to left, down and up columns to scramble the letters. Then, starting in the first row, the letters are taken in order to get the new ciphertext. For example, if the message needed to be enciphered was THE DOG RAN FAR, the Chinese cipher would look like this:
+
+                           R R G T
+                           A A O H
+                           F N D E
+                           
+The cipher text then reads: RRGT AAOH FNDE
+

cryptography/chinese_cipher/perl/chinese_cipher.pl

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+#!/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');