Language: Python Goal: implement decry
Language: Python
Goal: implement decryption in the attached code block
import argparse
import os
import time
import sys
import string
# Handle command-line arguments
parser = argparse.ArgumentParser()
parser.add_argument("-d", "--decrypt", help='Decrypt a file', required=False)
parser.add_argument("-e", "--encrypt", help='Encrypt a file', required=False)
parser.add_argument("-o", "--outfile", help='Output file', required=False)
args = parser.parse_args()
encrypting = True
try:
ciphertext = open(args.decrypt, "rb").read()
try:
plaintext = open(args.encrypt, "rb").read()
print("You can't specify both -e and -d")
exit(1)
except Exception:
encrypting = False
except Exception:
try:
plaintext = open(args.encrypt, "rb").read()
except Exception:
print("Input file error (did you specify -e or -d?)")
exit(1)
def lrot(n, d):
return ((n << d) & 0xff) | (n >> (8 - d))
if encrypting:
# Get the key
keybytes = bytes(os.urandom(8))
keyrotate = keybytes[0] % 7 + 1
keyxor = []
key = ""
# Rotate the key
for i in range(1, 8):
keyxor.append(ord(string.ascii_letters[keybytes[i] % len(string.ascii_letters)]))
key = key + chr(keyxor[i-1])
print("The key is %s rotated by %d bits." % (key, keyrotate))
ciphertext = []
for i in range(0, len(plaintext)):
ciphertext.append(lrot(plaintext[i], keyrotate) ^ keyxor[i % len(keyxor)])
with open(args.outfile, "wb") as output:
output.write(bytes(ciphertext))
output.close()
else:
print("Decryption is not implemented!")
exit(1)
Trending now
This is a popular solution!
Step by step
Solved in 3 steps with 3 images
