如何从文件中解码编码为 base64 的行？

Question

我需要解码文件中的行。

到目前为止，这是我的代码：

    def decode(self) -> list:
        """
        Decode file with key.

        For correct answer you have to convert file lines from base64 to utf-8.

        To decode one line you have to take a UNICODE value of a letter, subtract cipher step and take mod of 255.
        After that you have to convert that number back to a character.
        Example: key = 'test', decoded_data = "+%'"
        '+' -> (43 - 448) % 255 -> 'i' -> ... -> 'ice'

        :return: List of decoded lines
        """
        decoded_lines1 = []
        decoded_lines = []
        lines = self.read_code_from_file()
        for line in lines:
            decoded_lines.append(base64.b64decode(line).decode())
        for decoded_line in decoded_lines:
            for letter in decoded_line:
                decoded_lines1.append(chr((ord(letter) - sum([ord(i) for i in self.key])) % 255))
        return decoded_lines1

解码行：

[')-.7)-\x06\x06AOO', '-57)-0\x06\x06JASJAOOASJ', ')07)2\x06\x06AJSAJAJOAJJAAO',...]

我的 output 由于某种原因所有的字母都是单独的，下面 output 的一小部分在解码我的 output 后等于 decoded_lines 的第一个列表元素：

['-', '1', '2', ';', '-', '1', '\n', '\n', 'E', 'S', 'S', ...]

预计 output：

['-12;-1\n\nESS', ...]

有什么办法可以用逗号分隔行而不是用逗号分隔每个字母？ 非硬编码密钥等于 1016。

Answer 1

问题是你 append 每个字符，一个一个地解码到decoded_lines1当你做

.append(chr((ord(letter) - sum([ord(i) for i in self.key])) % 255))

相反，您想对decoded_line中的每个字符执行此操作，从所有解码字符中创建一个字符串，然后将该字符串append 到decoded_lines1 。

for decoded_line in decoded_lines:
    new_line = []
    for letter in decoded_line:
       new_line.append(chr((ord(letter) - sum([ord(i) for i in self.key])) % 255))
    decoded_lines1.append("".join(new_line))

但是您可以通过组合for line in lines和for decoded_line in decoded_lines循环来进一步简化代码：

def decode(self):
    decoded_lines = []
    lines = self.read_code_from_file()
    for line in lines:
        decoded_line = base64.b64decode(line).decode()
        new_line = []
        for letter in decoded_line:
            new_line.append(chr((ord(letter) - sum([ord(i) for i in self.key])) % 255))
        decoded_lines.append("".join(new_line))
    return decoded_lines

Answer 2

问题出在下面的代码中：

for decoded_line in decoded_lines:
    for letter in decoded_line:
        decoded_lines1.append(chr((ord(letter) - sum([ord(i) for i in self.key])) % 255))

在这里，您在将 append 解码行添加到列表中时逐个字母地附加到列表中。

所以，我将解码后的字母存储到一个字符串中，然后将 append 存储到列表中。

for decoded_line in decoded_lines:
            temp=""
            for letter in decoded_line:
                temp=temp+chr((ord(letter) - sum([ord(i) for i in self.key])) % 255)
            decoded_lines1.append(temp)

最终代码将如下所示：

def decode(self) -> list:
        """
        Decode file with key.

        For correct answer you have to convert file lines from base64 to utf-8.

        To decode one line you have to take a UNICODE value of a letter, subtract cipher step and take mod of 255.
        After that you have to convert that number back to a character.
        Example: key = 'test', decoded_data = "+%'"
        '+' -> (43 - 448) % 255 -> 'i' -> ... -> 'ice'

        :return: List of decoded lines
        """
        decoded_lines1 = []
        decoded_lines = []            
        lines = self.read_code_from_file()
        for line in lines:
            decoded_lines.append(base64.b64decode(line).decode())
        for decoded_line in decoded_lines:
            temp=""
            for letter in decoded_line:
                temp=temp+chr((ord(letter) - sum([ord(i) for i in self.key])) % 255)
            decoded_lines1.append(temp)                
        return decoded_lines1

Answer 3

你一行中只有一个词吗？ 它是一个句子吗？ 它由多个单词组成，那么你的第二个循环应该在单词上，然后第三个循环应该在字母上。 代码应该是这样的

def decode(self) -> list:
        """
        Decode file with key.

        For correct answer you have to convert file lines from base64 to utf-8.

        To decode one line you have to take a UNICODE value of a letter, subtract cipher step and take mod of 255.
        After that you have to convert that number back to a character.
        Example: key = 'test', decoded_data = "+%'"
        '+' -> (43 - 448) % 255 -> 'i' -> ... -> 'ice'

        :return: List of decoded lines
        """
        decoded_lines1 = []
        decoded_lines = []
        lines = self.read_code_from_file()
        for line in lines:
            decoded_lines.append(base64.b64decode(line).decode())
        for decoded_line in decoded_lines:
            for word in decoded_line.split():
                docoded_word=''
                for letter in word:
                    docoded_word+=(chr((ord(letter) - sum([ord(i) for i in self.key])) % 255))
                decoded_lines1.append(docoded_word)
        return (decoded_lines1)