Pycrypto:增加点击率模式

Question

仍然无法让这个工作.我的问题是关于如何使解密线工作.这是我写的:

class IVCounter(object):
    @staticmethod
    def incrIV(self):
        temp = hex(int(self, 16)+1)[2:34]
        return array.array('B', temp.decode("hex")).tostring()


def decryptCTR(key, ciphertext):

    iv = ciphertext[:32] #extracts the first 32 characters of the ciphertext

    #convert the key into a 16 byte string
    key = array.array('B', key.decode("hex")).tostring()

    print AES.new(key, AES.MODE_CTR, counter=IVCounter.incrIV(iv)).decrypt(ciphertext)
    return

我的错误信息是:

ValueError:'counter'参数必须是可调用对象

我只是无法弄清楚pycrypto是如何让我将第三个参数组织成新的.

有人可以帮忙吗？谢谢!

在实施以下建议后编辑新代码.还是卡住了!

class IVCounter(object):
    def __init__(self, start=1L):
        print start #outputs the number 1 (not my IV as hoped)
        self.value = long(start)

   def __call__(self):
        print self.value  #outputs 1 - need this to be my iv in long int form
        print self.value + 1L  #outputs 2
        self.value += 1L
        return somehow_convert_this_to_a_bitstring(self.value) #to be written

def decryptCTR(key, ciphertext):

    iv = ciphertext[:32] #extracts the first 32 characters of the ciphertext
    iv = int(iv, 16)

    #convert the key into a 16 byte string
    key = array.array('B', key.decode("hex")).tostring()

    ctr = IVCounter()
    Crypto.Util.Counter.new(128, initial_value = iv)

    print AES.new(key, AES.MODE_CTR, counter=ctr).decrypt(ciphertext)
    return

EDIT STILL无法让这个工作.非常沮丧,完全出于想法.这是最新的代码:(请注意,我的输入字符串是32位十六进制字符串,必须以两位数字对解释才能转换为长整数.)

class IVCounter(object):
    def __init__(self, start=1L):
        self.value = long(start)

    def __call__(self):
        self.value += 1L
        return hex(self.value)[2:34]

def decryptCTR(key, ciphertext):
    iv = ciphertext[:32] #extracts the first 32 characters of the ciphertext
    iv = array.array('B', iv.decode("hex")).tostring()

    ciphertext = ciphertext[32:]

    #convert the key into a 16 byte string
    key = array.array('B', key.decode("hex")).tostring()

    #ctr = IVCounter(long(iv))
    ctr = Crypto.Util.Counter.new(16, iv)

    print AES.new(key, AES.MODE_CTR, counter=ctr).decrypt(ciphertext)
    return

TypeError:CTR计数器函数返回的字符串长度不是16

Answer 1

在Python中,将函数视为对象是完全有效的.处理定义__call__(self, ...)为函数的任何对象也是完全有效的.

所以你想要的东西可能是这样的:

class IVCounter(object):
    def __init__(self, start=1L):
        self.value = long(start)
    def __call__(self):
        self.value += 1L
        return somehow_convert_this_to_a_bitstring(self.value)

ctr = IVCounter()
... make some keys and ciphertext ...
print AES.new(key, AES.MODE_CTR, counter=ctr).decrypt(ciphertext)

但是,PyCrypto为你提供了一个比纯Python更快的计数器方法:

import Crypto.Util.Counter
ctr = Crypto.Util.Counter.new(NUM_COUNTER_BITS)

ctr现在是一个有状态函数(同时也是一个可调用对象),每次调用它时它都会递增并返回其内部状态.然后你可以做

print AES.new(key, AES.MODE_CTR, counter=ctr).decrypt(ciphertext)

就像以前一样.

这是一个使用CTR模式下的Crypto.Cipher.AES和一个用户指定的初始化向量的工作示例:

import Crypto.Cipher.AES
import Crypto.Util.Counter

key = "0123456789ABCDEF" # replace this with a sensible value, preferably the output of a hash
iv = "0000000000009001" # replace this with a RANDOMLY GENERATED VALUE, and send this with the ciphertext!

plaintext = "Attack at dawn" # replace with your actual plaintext

ctr = Crypto.Util.Counter.new(128, initial_value=long(iv.encode("hex"), 16))

cipher = Crypto.Cipher.AES.new(key, Crypto.Cipher.AES.MODE_CTR, counter=ctr)
print cipher.encrypt(plaintext)