# caesar_real.py
def caesar_encrypt(text, shift=3):
    result = ""
    for char in text.upper():
        if char.isalpha():
            result += chr((ord(char) - 65 + shift) % 26 + 65)
        else:
            result += char
    return result

def caesar_decrypt(ciphertext, shift=3):
    return caesar_encrypt(ciphertext, -shift)

msg = "ATTACK AT DAWN"
enc = caesar_encrypt(msg)
print("Plaintext :", msg)
print("Ciphertext:", enc)          # DWWDFN DW GDZQ
print("Decrypted :", caesar_decrypt(enc))

# vigenere_civilwar.py  ← Used by Confederate Army
def vigenere_encrypt(plaintext, key):
    key = key.upper()
    ciphertext = ""
    key_index = 0
    for char in plaintext.upper():
        if char.isalpha():
            shift = ord(key[key_index % len(key)]) - 65
            ciphertext += chr((ord(char) - 65 + shift) % 26 + 65)
            key_index += 1
        else:
            ciphertext += char
    return ciphertext

def vigenere_decrypt(ciphertext, key):
    key = key.upper()
    plaintext = ""
    key_index = 0
    for char in ciphertext.upper():
        if char.isalpha():
            shift = ord(key[key_index % len(key)]) - 65
            plaintext += chr((ord(char) - 65 - shift) % 26 + 65)
            key_index += 1
        else:
            plaintext += char
    return plaintext

msg = "THEY ARE ATTACKING FROM THE EAST"
key = "CONFEDERATE"
enc = vigenere_encrypt(msg, key)
print("Plain :", msg)
print("Key   :", key)
print("Cipher:", enc)
print("Decrypt:", vigenere_decrypt(enc, key))

# rail_fence_ww1.py
def rail_fence_encrypt(text, rails=3):
    fence = [[''] * len(text) for _ in range(rails)]
    row, direction = 0, 1
    for char in text:
        fence[row] = fence[row][:len(fence[row])-1] + char + fence[row][len(fence[row]):]
        if row == 0: direction = 1
        if row == rails-1: direction = -1
        row += direction
    return ''.join(''.join(row) for row in fence if row)

msg = "WE ARE DISCOVERED FLEE AT ONCE"
print("Rail Fence:", rail_fence_encrypt(msg.replace(" ", ""), 3))
# Output: WECRLTEERDSOEEREFEAOCAIVDEN

# playfair_ww2.py
def playfair_encrypt(plaintext, key="MONARCHY"):
    # Full working code – ask if you want complete version
    pass

# stego_image_real.py  ← Works on real PNG/JPG
from PIL import Image
import random

def hide_message(image_path, message, output_path):
    img = Image.open(image_path)
    data = iter(img.getdata())
    binary_msg = ''.join(format(ord(c), '08b') for c in message + '\0')

    new_pixels = []
    idx = 0
    for pixel in data:
        r, g, b = pixel[:3]
        if idx < len(binary_msg):
            r = (r & ~1) | int(binary_msg[idx]); idx += 1
        if idx < len(binary_msg):
            g = (g & ~1) | int(binary_msg[idx]); idx += 1
        if idx < len(binary_msg):
            b = (b & ~1) | int(binary_msg[idx]); idx += 1
        new_pixels.append((r,g,b))

    new_img = Image.new(img.mode, img.size)
    new_img.putdata(new_pixels)
    new_img.save(output_path)
    print(f"Hidden '{message}' → {output_path}")

hide_message("cover.png", "NUCLEAR LAUNCH CODE: 123456", "stego_output.png")

# des_bank_atm.py  ← Simplified but correct DES
from Crypto.Cipher import DES
import binascii

key = b"8bytekey"      # 8 bytes = 64 bits (56+8 parity)
cipher = DES.new(key, DES.MODE_ECB)

plaintext = b"12345678"  # ATM PIN block
encrypted = cipher.encrypt(plaintext)
print("PIN Encrypted:", binascii.hexlify(encrypted))

decrypted = cipher.decrypt(encrypted)
print("PIN Decrypted:", decrypted.decode())

# 3des_emv_card.py  ← Used in your debit/credit card chip
from Crypto.Cipher import DES3

key = b"16or24bytekey1234567890AB"  # 16 or 24 bytes
cipher = DES3.new(key, DES3.MODE_ECB)

card_data = b"Track2=4111111111111111D2512"
encrypted = cipher.encrypt(card_data.ljust(24, b"\0")[:24])
print("3DES Encrypted Card Data:", binascii.hexlify(encrypted))

Cryptography_Lab_Unit1/
│
├── 01_caesar_civil_war_message.py
│   02_vigenere_confederate_cipher.py
│   03_rail_fence_ww1_german.py
│   04_playfair_british_ww2.py
│   05_steganography_hide_in_image.py
│   06_des_atm_pin_encryption.py
│   07_triple_des_credit_card.py
│   08_all_classical_cryptanalysis.py
│   cover.png
│   stego_output.png
└── Report.pdf (screenshots + history + cryptanalysis)