Data commit

Task/Vigen-re-cipher/Elixir/vigen-re-cipher.elixir

@@ -0,0 +1,28 @@
+defmodule VigenereCipher do
+  @base  ?A
+  @size  ?Z - @base + 1
+
+  def encrypt(text, key), do: crypt(text, key, 1)
+
+  def decrypt(text, key), do: crypt(text, key, -1)
+
+  defp crypt(text, key, dir) do
+    text = String.upcase(text) |> String.replace(~r/[^A-Z]/, "") |> to_char_list
+    key_iterator = String.upcase(key) |> String.replace(~r/[^A-Z]/, "") |> to_char_list
+                   |> Enum.map(fn c -> (c - @base) * dir end) |> Stream.cycle
+    Enum.zip(text, key_iterator)
+    |> Enum.reduce('', fn {char, offset}, ciphertext ->
+         [rem(char - @base + offset + @size, @size) + @base | ciphertext]
+       end)
+    |> Enum.reverse |> List.to_string
+  end
+end
+
+plaintext = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!"
+key = "Vigenere cipher"
+ciphertext = VigenereCipher.encrypt(plaintext, key)
+recovered  = VigenereCipher.decrypt(ciphertext, key)
+
+IO.puts "Original: #{plaintext}"
+IO.puts "Encrypted: #{ciphertext}"
+IO.puts "Decrypted: #{recovered}"