栅栏加密 python 实现

栅栏加密（Rail Fence Cipher）是一种经典的加密方法，它通过将文本按照Z字形排列在若干行上，然后按行读取来形成密文。这种加密方式比较简单，适用于简单的文本加密。

在Python中实现栅栏加密的一个简单示例可以如下所示：

def encode_rail_fence(text, num_rails):
    # 将文本按字符分割成列表
    chars = [c for c in text]
    # 计算每行的字符数量
    cycle_length = num_rails - 1
    encoded_chars = []

    for rail in range(num_rails):
        step = cycle_length * 2 if rail % 2 == 0 else 1
        index = 0
        while index < len(chars):
            encoded_chars.append(chars[index])
            index += step
            if rail > 0 and rail < num_rails - step
                if next_index < len(chars):
                    index = next_index

    # 将加密后的字符列表合并成字符串
    return ''.join(encoded_chars)

def decode_rail_fence(encoded_text, num_rails):
    chars = [c for c in encoded_text]
    cycle_length = num_rails - 1
    decoded_chars = [''] * len(chars)

    for rail in range(num_rails):
        step = cycle_length * 2 if rail % 2 == 0 else 1
        index = 0
        while index < len(chars):
            decoded_chars[index] = chars[index]
            index += step
            if rail > 0 and rail < num_rails - 1:
                next_index = index + cycle_length * 2 - step
                if next_index < len(chars):
                    index = next_index

    return ''.join(decoded_chars)

# 使用示例
text = "hello world"
num_rails = 3
encoded_text = encode_rail_fence(text, num_rails)
print("Encoded Text:", encoded_text)

decoded_text = decode_rail_fence(encoded_text, num_rails)
print("Decoded Text:", decoded_text)

在上面的代码中，`encode_rail_fence` 函数负责将文本按照栅栏加密的方式进行加密，而 `decode_rail_fence` 函数则将密文解密回原文。