递归迭代每个字符组合

Question

预期结果:

该程序采用哈希密码作为输入; 这被传递给decrypt函数.该函数迭代每个混合大小写的n字母组合,对每个这样的字符串进行散列.如果找到与输入匹配的内容,则会打印出未散列的密码; 否则,它会退出.

实际结果:

函数仅针对当前迭代中的最后一个字母迭代每个混合大小写字母.

问题描述:

我正在尝试用Python实现一个简单的暴力DES加密密码破解程序.我使用了很多for循环实现了4个字符的密码实现,但现在我想使用递归来重构一段长度.如何迭代每个字符组合,从1-char组合到4个字符的字符串组合？

我想用这一行:

            password[i] = string.ascii_letters[j]

但我得到这个错误:

TypeError: 'str' object does not support item assignment

代码段:

def decrypt(encryptedText):
    # reference global variable
    global password
    # check curr password guess length
    pwdlen = len(password)

    if pwdlen >= 4:
        print("Password is longer than 4 characters, exiting...")
        exit(2)

    # debug lines
    print("password is {}".format(password))
    print("length: {}".format(pwdlen))
    time.sleep(2)

    # first two characters is salt
    salt = encryptedText[:2]

    # Check hashes for every combination of strings and compare them
    # starts with last char
    for i in range(pwdlen, 0, -1):
        for j in range(0, len(string.ascii_letters)):
            password = string.ascii_letters[:pwdlen] + string.ascii_letters[j]
            hashed = crypt.crypt(password, salt)

            # debug line
            print(password)

            # if found - print password and exit
            if hashed == encryptedText:
                print(password)
                exit(0)

    # this makes recursion go through +1 char combinations on every iteration
    password = (pwdlen + 1) * 'a'

    return decrypt(encryptedText)

Answer 1

字符串是不可变的.您不能为字符串的一部分分配新值.相反,您必须构建一个新值并将其分配给原始变量.例如:

# password[i] = string.ascii_letters[j]
password = password[:i] + string.ascii_letters[j] + password[i+1:]

其次,通过使用itertools包生成所需的所有排列,您可以做得更好.例如,生成的产物asci_letters只要你想了很多次,通过步骤加入这些字母序列.