问题描述
在 php 中有没有办法从字符串中给出唯一的散列，但散列仅由数字组成?
In php is there a way to give a unique hash from a string, but that the hash was made up from numbers only?
示例:
return md5(234); // returns 098f6bcd4621d373cade4e832627b4f6
但我需要
return numhash(234); // returns 00978902923102372190
(20 numbers only)
这里的问题是我希望散列很短.
the problem here is that I want the hashing to be short.
好的，让我在这里解释一下背景故事.我有一个网站，每个注册人都有一个 ID，我还需要一个 ID 供该人使用和交换(因此不能太长)，到目前为止 ID 编号为 00001、00002、00003 等...
edit: OK let me explain the back story here. I have a site that has a ID for every registered person, also I need a ID for the person to use and exchange (hence it can't be too long), so far the ID numbering has been 00001, 00002, 00003 etc...
- 这会让一些人看起来更重要
- 这会显示我不想透露的应用程序信息.
要修复第 1 点和第 2 点，我需要隐藏"该数字，同时保持其唯一性.
To fix point 1 and 2 I need to "hide" the number while keeping it unique.
基于https://stackoverflow.com/a/23679870/175071的代码的数字哈希函数p>
Numeric hash function based on the code by https://stackoverflow.com/a/23679870/175071
/**
* Return a number only hash
* https://stackoverflow.com/a/23679870/175071
* @param $str
* @param null $len
* @return number
*/
public function numHash($str, $len=null)
{
$binhash = md5($str, true);
$numhash = unpack('N2', $binhash);
$hash = $numhash[1] . $numhash[2];
if($len && is_int($len)) {
$hash = substr($hash, 0, $len);
}
return $hash;
}
// Usage
numHash(234, 20); // always returns 6814430791721596451
推荐答案
有一些很好的答案，但对我来说，这些方法似乎很愚蠢.
他们首先强制 php 创建一个 Hex 数字，然后将其转换回 (hexdec) 在 BigInteger 中，然后将其缩减为多个字母......这是很多工作！
There are some good answers but for me the approaches seem silly.
They first force php to create a Hex number, then convert this back (hexdec) in a BigInteger and then cut it down to a number of letters... this is much work!
为什么不呢
将哈希读取为二进制:
$binhash = md5('[input value]', true);
然后使用
$numhash = unpack('N2', $binhash); //- or 'V2' for little endian
将其转换为两个 INT($numhash 是两个元素的数组).现在您可以简单地使用 AND 操作来减少数字中的位数.例如:
to cast this as two INTs ($numhash is an array of two elements). Now you can reduce the number of bits in the number simply using an AND operation. e.g:
$result = $numhash[1] & 0x000FFFFF; //- to get numbers between 0 and 1048575
但要注意碰撞！减少数字意味着增加两个不同[输入值]具有相同输出的概率.
But be warned of collisions! Reducing the number means increasing the probability of two different [input value] with the same output.
我认为更好的方法是使用带有 Bijectiv 函数的ID-Crypting".所以不会发生碰撞！对于最简单的类型，只需使用 Affine_cipher
I think that the much better way would be the use of "ID-Crypting" with a Bijectiv function. So no collisions could happen! For the simplest kind just use an Affine_cipher
最大输入值范围为 0 到 25 的示例:
Example with max input value range from 0 to 25:
function numcrypt($a)
{
return ($a * 15) % 26;
}
function unnumcrypt($a)
{
return ($a * 7) % 26;
}
输出:
numcrypt(1) : 15
numcrypt(2) : 4
numcrypt(3) : 19
unnumcrypt(15) : 1
unnumcrypt(4) : 2
unnumcrypt(19) : 3
例如
$id = unnumcrypt($_GET('userid'));
... do something with the ID ...
echo '<a href="do.php?userid='. numcrypt($id) . '"> go </a>';
当然这是不安全的，但如果没有人知道用于加密的方法，那么就没有安全原因，那么这种方式更快且碰撞安全.
of course this is not secure, but if no one knows the method used for your encryption then there are no security reasons then this way is faster and collision safe.
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