return xored
end
end
+
+redef class CString
+ # In-place XOR `self` with `key`
+ fun xor(key: CString, len: Int, key_length: Int, key_offset: nullable Int) do
+ if key_offset == null then key_offset = 0
+
+ var key_pos = key_offset % key_length
+
+ for i in [0 .. len[ do
+ self[i] = key[key_pos] ^ self[i]
+ key_pos += 1
+ if key_pos >= key_length then key_pos = 0
+ end
+ 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: Int = 0
+
+ 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