lib/crypto: Introduce XOR cipher management classes

Introduced Single-byte XOR cipher management class
Introduced Repeating-key XOR cipher management class

Signed-off-by: Philippe Pepos Petitclerc <ppeposp@gmail.com>

diff --git a/lib/crypto/xor_ciphers.nit b/lib/crypto/xor_ciphers.nit
index fefae4b..1c4807c 100644 (file)
--- a/lib/crypto/xor_ciphers.nit
+++ b/lib/crypto/xor_ciphers.nit
@@ -31,3 +31,58 @@ redef class Bytes
                return xored
        end
 end
+
+# Base class to modelize cryptographic ciphers
+abstract class Cipher
+
+       # Encrypted data
+       var ciphertext = new Bytes.empty is writable
+
+       # Unencrypted data
+       var plaintext = new Bytes.empty is writable
+
+       # Encrypt plaintext and populate `self.ciphertext`
+       fun encrypt is abstract
+
+       # Decrypt ciphertext and populate `self.plaintext`
+       fun decrypt is abstract
+
+end
+
+# Simple XOR cipher where the whole plaintext is XORed with a single byte.
+class SingleByteXorCipher
+       super Cipher
+
+       # Cryptographic key used in encryption and decryption.
+       var key: Byte = 0.to_b
+
+       redef fun encrypt do
+               var key_bytes = new Bytes.with_capacity(1)
+               key_bytes.add(key)
+               ciphertext = plaintext.xorcipher(key_bytes)
+       end
+
+       redef fun decrypt do
+               var key_bytes = new Bytes.with_capacity(1)
+               key_bytes.add(key)
+               plaintext = ciphertext.xorcipher(key_bytes)
+       end
+end
+
+# XOR cipher where the key is repeated to match the length of the message.
+class RepeatingKeyXorCipher
+       super Cipher
+
+       # Cryptographic key used in encryption and decryption.
+       var key = new Bytes.empty
+
+       redef fun encrypt do
+               assert key.length > 0
+               ciphertext = plaintext.xorcipher(key)
+       end
+
+       redef fun decrypt do
+               assert key.length > 0
+               plaintext = ciphertext.xorcipher(key)
+       end
+end