cyber-security-resources/crypto/challenges/01_Classic_Caesar_Cipher.md
2023-08-15 09:43:27 -04:00

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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.