lab

uczelnia/1_semestr/wprowadzenie_do_informatyki/laby/szyfrhilla.py

@@ -1,50 +1,82 @@
 import numpy as np
 
+
 def letter_to_num(letter):
     return ord(letter.upper()) - ord('A')
 
+
 def num_to_letter(num):
     return chr(num + ord('A'))
 
 
-def cipher(text: str):
-    k = np.array([[3, 3], [2, 5]])
+def matrix_mod_inv(key):
+    det = int(round(np.linalg.det(key)))
+    det_mod = det % 26
+    det_inv = pow(det_mod, -1, 26)
+
+    adj = np.array([[key[1, 1], -key[0, 1]],
+                    [-key[1, 0],  key[0, 0]]])
+
+    return (det_inv * adj) % 26
+
+
+def cipher(text: str, key: int):
     text_upper = text.upper().replace(' ', '')
 
+    if not validate_key(key):
+        print("Macierz klucz nie jest odwracalna, wybierz inną")
+        exit(1)
+
     if len(text_upper) % 2 != 0:
         text_upper += "X"
 
-    text_number = [letter_to_num(letter) for letter in text_upper]
+    nums = [letter_to_num(letter) for letter in text_upper]
+    mat = np.array(nums).reshape(-1, 2).T
 
-    text_matrix = np.array(text_number).reshape(-1, 2).T
+    c = (key @ mat) % 26
+    return "".join(num_to_letter(n) for n in c.T.flatten())
 
-    c = (k @ text_matrix) % 26
 
-    cipher_text = ''.join(num_to_letter(num) for num in c.T.flatten())
-
-    return cipher_text
-
-def decipher(text: str):
-    k = np.array([[3, 3], [2, 5]])
-    k_inv = np.linalg.inv(k)
+def decipher(text: str, key: int):
     text_upper = text.upper().replace(' ', '')
+    if not validate_key(key):
+        print("Macierz klucz nie jest odwracalna, wybierz inną")
+        exit(1)
+
+    key_inv = matrix_mod_inv(key)
 
     if len(text_upper) % 2 != 0:
         text_upper += "X"
 
-    text_number = [letter_to_num(letter) for letter in text_upper]
+    nums = [letter_to_num(letter) for letter in text_upper]
+    mat = np.array(nums).reshape(-1, 2).T
 
-    text_matrix = np.array(text_number).reshape(-1, 2).T
+    p = (key_inv @ mat) % 26
+    return "".join(num_to_letter(n) for n in p.T.flatten())
 
-    c = (k_inv @ text_matrix) % 26
 
-    cipher_text = ''.join(num_to_letter(num) for num in c.T.flatten())
+def validate_key(key) -> bool:
+    key = np.asarray(key)
+
+    if key.shape != (2, 2):
+        return False
+
+    if not np.all((0 <= key) & (key < 26)):
+        return False
+
+    det = int(round(np.linalg.det(key)))
+    det_mod = det % 26
+
+    return np.gcd(det_mod, 26) == 1
 
-    return cipher_text
 
 if __name__ == "__main__":
-    test_text = "Test"
-    cipher = cipher(test_text)
-    #decipher = decipher(cipher)
-    print("Text: ", test_text)
-    print("cipher: ", cipher)
+    key = np.array([[3, 3],
+                    [2, 5]])
+
+    test_text = "TEST"
+    ciphered_text = cipher(test_text, key)
+    deciphered_text = decipher(ciphered_text, key)
+    print("Text:", test_text)
+    print("Cipher:", ciphered_text)
+    print("Decipher:", deciphered_text)