This lecture teaches how modern systems protect data, assuming that there are loop holes in the system architecture and leakages.

I will start with what new you can know from here:

Before that if you think you want to brush up your concepts quick: Refer this : Topic-wise explanation:

So after brushing up we have our Ceasar code which decrypts the things:

import string
ENGLISH_FREQ = {
    'e': 12.0, 't': 9.1, 'a': 8.1, 'o': 7.5,
    'i': 7.0, 'n': 6.7, 's': 6.3, 'h': 6.1,
    'r': 6.0, 'd': 4.3, 'l': 4.0,
    'c': 2.8, 'u': 2.8, 'm': 2.4,
    'w': 2.4, 'f': 2.2, 'g': 2.0,
    'y': 2.0, 'p': 1.9, 'b': 1.5,
    'v': 1.0, 'k': 0.8, 'j': 0.15,
    'x': 0.15, 'q': 0.10, 'z': 0.07
}

def caesar_decrypt(cipher, shift):
    result = ''
    for char in cipher:
        if char.isalpha():
            offset = 65 if char.isupper() else 97
            result += chr((ord(char) - offset - shift) % 26 + offset)
        else:
            result += char
    return result

def score_text(text):
    score = 0
    for char in text.lower():
        if char in ENGLISH_FREQ:
            score += ENGLISH_FREQ[char]
    return score

cipher = input("Enter your Cipher: ")

res = []

for shift in range(1, 26):
    decrypted = caesar_decrypt(cipher, shift)
    score = score_text(decrypted)
    res.append((score, shift, decrypted))

res.sort(reverse=True)

for score, shift, text in res[:]:
    print(f"Shift {shift} | Score {score:.2f} | {text}")

Topic-wise explanation: