加密/解密 [英] Encryption / Decryption Sugestions

问题描述

例如：

  $ str ='Hello World！'; 
 encrypt（$ str）; //返回：abc123//固定长度的字符。 
 decrypt（'abc123'）; //返回：Hello World！//原始字符串的内容。 
  

以上是在php中

可以任何一种计算机语言：

只要修正了，可以是固定号码

相同：32个字符，64个字符或X个字符。

我已经研究了一点，看起来很难或不可见。
但是你永远都不知道我以为可能会被worthed询问

如果你不要求你没有得到:) thnx

是的，如果您想要加密的字符数量有上限X ，这是可能的。只需使用任何加密算法加密，然后将结果填充到 X 字符。

如果没有上限，这是不可能的信息理论（你必须以某种方式存储无限数量的字符作为有限数量的[加密]字符，这是不可能的）。要了解原因，请查看鸽子原则。

Is there a way to encrypt any string or file of any length and return a key with a fixed length.

e.g:

$str = 'Hello World!'; 
encrypt($str);//returns: "abc123"//a fixed length of characters.
decrypt('abc123');//returns: "Hello World!"//the contents of the original string.

above is in php

Can be any computer language:

Can be any fixed number as long as it's fixed

by fixed i mean always the same: 32 character, 64 characters or X characters.

I have researched a little and it looks like it's hard or imposible. but you never know i thought it might be worthed asking

if you dont ask you don't get :) thnx

解决方案

Yes, this is possible if there is an upper bound X for the number of characters you want to encrypt. Just encrypt using any encryption algorithm, then pad the result to X characters.

If there is no upper bound, this is impossible for reasons of information theory (you would have to somehow store an unlimited number of characters as a limited number of [encrypted] characters, which is not possible in general). To understand why, look up the pigeonhole principle.

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