add caesar cipher algorithm

dori-dev · dori-dev · commit 3d067d5b5923 · 2022-08-02T09:51:04.000+04:30
diff --git a/ciphers/caesar_cipher.py b/ciphers/caesar_cipher.py
@@ -0,0 +1,46 @@
+"""
+caesar cipher algorithm, implement in python
+complexity: O(n)
+"""
+
+from string import ascii_letters
+
+
+def encrypt(input_string: str, key: int) -> str:
+    alpha = ascii_letters
+    result = ""
+    for letter in input_string:
+        if letter not in alpha:
+            result += letter
+            continue
+        new_key = (alpha.index(letter) + key) % len(alpha)
+        result += alpha[new_key]
+    return result
+
+
+def decrypt(input_string: str, key: int) -> str:
+    key *= -1
+    return encrypt(input_string, key)
+
+
+def brute_force(input_string: str) -> dict:
+    alpha = ascii_letters
+    key = 1
+    brute_force_data = {}
+    while key <= len(alpha):
+        result = decrypt(input_string, key)
+        brute_force_data[key] = result
+        key += 1
+    return brute_force_data
+
+
+if __name__ == '__main__':
+    # encrypt & decrypt mohammad dori
+    print(encrypt('mohammad dori', 8))
+    print(decrypt('uwpiuuil lwzq', 8))
+    # encrypt & decrypt dori-dev
+    print(encrypt('dori-dev', 8))
+    print(decrypt('lwzq-lmD', 8))
+    # return brute force data for lwzq-lmD encrypted text
+    # and find the key `8` and true text `dori-dev`
+    print(brute_force('lwzq-lmD'))
