将 Java BigInteger 减少为固定长度的较小数字

发布于 2025-01-08 14:44:10 字数 743 浏览 2 评论 0原文

我正在尝试实现一个随机数生成器系统；本质上，我正在读取 SHA1 哈希，然后将其转换为 BigInteger 值：

String start = "abc";
String hash = utils.SHA1(start); //Generates an SHA1 hash of the string
byte[] bytes = hash.getBytes();
BigInteger big = new BigInteger(bytes);

此代码生成一个 BigInteger，其值为：

811203900027758629330492243480887228261034167773619203962320290854945165232584286910163772258660

我需要以某种方式做的事情（这就是我感到困惑的地方），是将数字减少为一个短得多的数字，具有固定的小数位数。

结合使用模算术和 Java Math API 函数，是否有一种明智的方法可以将此数字减少为 3 位数字。或者我选择的任何其他长度的数字。

目前，我只是简单地将这个巨大的数字转换为字符串，然后获取我想要的数字长度的子字符串。然而我对此并不完全满意，因为我得到的数字不是那么随机，因为范围有点限制在 3 位数字。

这样做的全部目的是为了将新生成的随机 x 位数字转换为基数为 36 的字符串，其中还包括 ASCII 字母字符。

任何信息或建议将不胜感激。

谢谢！！

原文

I'm attempting to implement a random number generator system; essentially I'm reading in an SHA1 hash, which then gets converted into a BigInteger value:

String start = "abc";
String hash = utils.SHA1(start); //Generates an SHA1 hash of the string
byte[] bytes = hash.getBytes();
BigInteger big = new BigInteger(bytes);

This code generates a BigInteger with a value of:

811203900027758629330492243480887228261034167773619203962320290854945165232584286910163772258660

What I need to somehow do (and this is where I get confused), is reduce that number into a much shorter number with a fixed number of decimal places.

Using a combination of modular arithmetic and Java Math API functions, is there a sensible way of reducing this number down into a 3 digit number. Or any other length of number I choose.

At the moment I'm just simply converting that huge number into a String, and then taking a substring of the length of number I want. However I'm not entirely happy with this as the numbers I get aren't that random, as the range is somewhat limited with 3 digits.

The whole purpose of this is for the newly generated random x digit number to be then converted into a string using a radix of 36, to also include ASCII alphabet characters.

Any information or advice would be greatly appreciated.

Thanks!!

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