Create 01_Classic_Caesar_Cipher.md

crypto/challenges/01_Classic_Caesar_Cipher.md

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+# Challenge 1: Caesar Cipher Shift
+
+**Challenge Text:**
+```
+Sifnz ebjnt, zpv ibwf cffo difdlfe! Dpvme zpv efdszqujpo uijt tfdsfu nfttbhf?
+```
+
+**Instructions:**
+1. Analyze the frequency of the letters, or use a brute-force approach to find the shift value.
+2. Write a program or manually shift the letters to decrypt the message, applying the reverse shift.
+3. Provide the original text.
+
+### Answer:
+
+The Caesar cipher is a type of substitution cipher in which each character in the plaintext is 'shifted' a certain number of places down or up the alphabet. In this particular case, the shift value is 1.
+
+**Decrypted Text:**
+```
+Rhemy dakim, you have been checked! Could you decrypting this secret message?
+```
+
+You can also use these code examples in Python to decrypt the message:
+
+```python
+def decrypt_caesar(ciphertext, shift):
+    decrypted = ""
+    for char in ciphertext:
+        if char.isalpha():
+            shifted = ord(char) - shift
+            if char.islower():
+                if shifted < ord('a'):
+                    shifted += 26
+            elif char.isupper():
+                if shifted < ord('A'):
+                    shifted += 26
+            decrypted += chr(shifted)
+        else:
+            decrypted += char
+    return decrypted
+
+ciphertext = "Sifnz ebjnt, zpv ibwf cffo difdlfe! Dpvme zpv efdszqujpo uijt tfdsfu nfttbhf?"
+shift = 1
+decrypted_text = decrypt_caesar(ciphertext, shift)
+print(decrypted_text)
+```
+
+This challenge serves as a fun and educational introduction to the field of cryptography, allowing you to explore basic decryption techniques. Try the next challenge.