如何解密RC2密文？

Question

的Python 3.5，pycrypto 2.7a1，Windows中，RC2加密

例子：

print('Введите текс, который хотите зашифровать:') 
text = input() 

with open('plaintext.txt', 'w') as f: 
    f.write(text) 

key = os.urandom(32) 

with open('rc2key.bin', 'wb') as keyfile: 
    keyfile.write(key) 

iv = Random.new().read(ARC2.block_size) 

cipher = ARC2.new(key, ARC2.MODE_CFB, iv) 
ciphertext = iv + cipher.encrypt(bytes(text, "utf-8")) 

with open('iv.bin', 'wb') as f: 
    f.write(iv) 

with open('ciphertext.bin', 'wb') as f: 
    f.write(ciphertext) 

print(ciphertext.decode("cp1251")) 

而且我想知道我怎麼能解密這個文本，我試過了，但不能這樣做。

我嘗試解密：

os.system('cls') 
print('Дешифруем значит') 

with open('ciphertext.bin', 'rb') as f: 
    ciphertext = f.read() 

with open('rc2key.bin', 'rb') as f: 
    key = f.read() 

with open('iv.bin', 'rb') as f: 
    iv = f.read() 

ciphertext = ciphertext.decode('cp1251') 
iv = iv.decode('cp1251') 

text = ciphertext.replace(iv, '') 
text = cipher.decrypt(text) 

with open('plaintext.txt', 'w') as f: 
    f.write(text) 

print(text.decode("ascii")) 

但我明白，我需要密碼變量，我不能將它保存爲.txt或.bin文件，以便爲什麼我尋求幫助。

Answer 1

IV是一個非祕密值，通常寫在密文前面。既然，你已經做到了，你不需要編寫額外的IV文件。 RC2的塊大小爲64位，所以IV總是8個字節長。

with open('ciphertext.bin', 'rb') as f: 
    ciphertext = f.read() 

with open('rc2key.bin', 'rb') as f: 
    key = f.read() 

iv = ciphertext[:ARC2.block_size] 
ciphertext = ciphertext[ARC2.block_size:] 

cipher = ARC2.new(key, ARC2.MODE_CFB, iv) 
text = cipher.decrypt(ciphertext).decode("utf-8") 

with open('plaintext.txt', 'w') as f: 
    f.write(text) 

print(text) 

其他問題：

• 不要簡單地解碼二進制數據，如密文，密鑰或IV，因爲這些是最有可能不能打印。

• 如果您正在做不同的事情，請勿重複使用相同的cipher對象。解密需要一個新鮮初始化的對象ARC2。