php - disagreeing md5 hashes of same string, with example

Question

This is getting me crazy, my md5's don't agree. I have this string:

The Combinations Generator is a tool that allows you to easily create a series of combinations by selecting the related attributes. For example, if you're selling t-shirts in three different sizes and two different colors, the generator will create six combinations for you.

When I hash it on my computer using the md5 function (with php 5.5.0) it produces the following hash: 422f3f656e1a5f95e8b5cf7565d815b5

http://www.miraclesalad.com/webtools/md5.php agrees with my computer's result.

http://www.md5.cz/ disagrees with both my computer and miraclesalad.

This string/md5 pair was initially computed by another computer which also gives the same result as md5.cz.

I read about encoding issues (although the string doesn't contain any non ASCII characters), so I tried the following code on my computer:

<?php

$str = "The Combinations Generator is a tool that allows you to easily create a series of combinations by selecting the related attributes. For example, if you're selling t-shirts in three different sizes and two different colors, the generator will create six combinations for you.";

echo "$str<BR/>";
echo md5($str)."<BR/>";
echo md5(utf8_encode($str))."<BR/>";
echo md5(utf8_decode($str))."<BR/>";


die();

The output is:

The Combinations Generator is a tool that allows you to easily create a series of combinations by selecting the related attributes. For example, if you're selling t-shirts in three different sizes and two different colors, the generator will create six combinations for you.

422f3f656e1a5f95e8b5cf7565d815b5

422f3f656e1a5f95e8b5cf7565d815b5

422f3f656e1a5f95e8b5cf7565d815b5

So it is not about utf8.

Any idea what's happening?

Answer 1

我最好的猜测是它与“you're”一词中的 ' 标记和字符编码有关。如果您删除该报价，两个站点都会报告相同的 md5。

Answer 2

我尝试将上面的字符串逐步提供给您在问题中链接到的两个站点，事实证明，如果您正在销售 T 恤，则在 md5.cz 处破坏生成器的字符是撇号。

如果在将特殊字符的字符串提供给哈希器之前将其剥离，可能会使用 urlencode() 之类的方法保留字符串的唯一性，那么您应该获得任何字符串的匹配哈希。

Answer 3

字符串必须完全相同，包括空格。可能这些站点正在使用一些转换，例如 trim() 或 stripslashes()。仅当字符串准确时， md5 才会返回相同的值。

Answer 4

md5 是 md5。这里的所有都是它的。如果您从不同的（非错误的）实现中获得不同的哈希值，那么您将输入不同的输入。请记住，如果输入甚至略有不同，md5 的设计目的是产生截然不同的输出。一个测试字符串末尾的单个空白字符（制表符、换行符等）将完全破坏您预期的哈希值，因为您输入了不同的输入。