Implement process_block, binary_strings_xor

s_des.py

@@ -11,7 +11,6 @@ class SDES:
             key_length (int): Length of keys that will be used for encryption/decryption
         """
         # SDES is a block-cipher algorithm, uses blocks of size 12 bits
-            # You can change this default value from here directly, and it'll applied to the whole code
         self.block_size = 12
 
         # SDED uses a fixed-length key (8bits- key) for each iteration
@@ -164,3 +163,22 @@ class SDES:
         blocks = []
         blocks = [binary_text[i:i+self.block_size] for i in range(0, len(binary_text), self.block_size)]
         return blocks
+    
+    def process_block(self, key: str, round_number: int, old_block: str) -> str:
+        L_old, R_old = old_block[0:self.block_size/2, self.block_size/2, self.block_size]
+        L_new = R_old
+        round_key = self.get_round_key(key, round_number)
+        R_new = self.f(round_key, R_old)
+        R_new = self.binary_strings_xor(R_new, L_old)
+        new_block = ''
+        new_block += L_new
+        new_block += R_new
+        return new_block
+
+    def binary_strings_xor(self, binary_string_1: str, binary_string_2: str) -> str:
+        num1 = int(binary_string_1, 2)
+        num2 = int(binary_string_2, 2)
+        xor_result = num1 ^ num2
+        xor_result_str = bin(xor_result)[2:]
+        xor_result_str = xor_result_str.zfill(len(binary_string_1))
+        return xor_result_str