SHA512在PHP中生成随机数 [英] SHA512 to generate random numbers in PHP

问题描述

我正在使用$blockhash[$i] = rand().time().rand()

然后，对于该数组中的每个随机数，我计算对应的SHA512

Then, for each random number in that array I calculate the correspondent SHA512

$SecretKey = "60674ccb549f1988439774adb82ff187e63a2dfd403a0dee852e4e4eab75a0b3";
$sha = hash_hmac('sha512', $value, $SecretKey);

将其拆分:

$pool  = str_split($sha, 2);

然后我从$ pool数组中获得第一个数字，将十六进制转换为dec并将其限制在1到50之间:

Then I get the first number from the $pool array, convert hex to dec and limit it within 1 and 50:

$dec = hexdec($pool[0]) % 50 + 1;

问题在于数字不是那么随机，我也不知道为什么.我正在计算每个数字从1到50的频率，但是数字1,2,3,4,5和6比其他数字经常出现.见图

The problem is that the numbers are not that random and I don't know why. I'm counting the frequency for each number from 1 to 50 but the numbers 1,2,3,4,5 and 6 are coming up often than the others. See graph

为什么会发生这种情况以及如何解决?谢谢！

Why is this happening and how to fix it? Thanks!

推荐答案

由于从哈希中获取两个十六进制数字，您获得1-6的频率更高.那是一个字节，因此它可以存储从0到255的值.然后，使用模50.结果，您得到范围0-49，50-99，100-149，150-199，200-249和... 250-255.这最后一个是您的结果中1-6普遍存在的原因.

You get 1-6 more often because you fetch two hexadecimal digits from the hash. That's one byte, so it can store values from 0 to 255. Then you use modulo 50. In result you get ranges 0-49, 50-99, 100-149, 150-199, 200-249 and... 250-255. This last one is responsible for extra prevalence of 1-6 in your results.

解决方案:只需使用mt_rand(1,50);

如果您确实需要将数字从0-255范围转换为1-50范围，则解决方案是缩放和舍入.

If you really need to convert a number from 0-255 range to 1-50 range, the solution would be scaling and rounding.

$number = round(($byteValue)/(255/49))+1; 

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