类似于/dev/urandom并带有可配置的种子吗? [英] Something similar to /dev/urandom with configurable seed?

问题描述

我来自/dev/urandom 的 dd ，以便创建具有随机内容的文件.这很好用，但是我希望以后可以通过使用相同的种子再次运行PRNG来重现文件内容.是否有任何可播种的PRNG公开了字符设备?

I'm dd'ing from /dev/urandom in order to create files with random contents. This works well, but I would like to be able to reproduce the file contents at some later point by running the PRNG again with the same seed. Is there any seedable PRNG which exposes a character device?

我正在使用最新的Linux 3.X内核.

I'm using recent Linux 3.X kernels.

推荐答案

/dev/urandom 旨在尽可能地不可预测.听起来您想要一个更常规的种子式伪随机数生成器.

/dev/urandom is designed to be as unpredictable as possible. It sounds like you want a more conventional seeded pseudorandom number generator.

这是我刚用C写的:

#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
    char *endptr;
    unsigned long int seed;

    if (argc != 2 || *argv[1] == '\0') {
        fprintf(stderr, "usage: %s seed\n", argv[0]);
        return EXIT_FAILURE;
    }
    errno = 0;
    seed = strtoul(argv[1], &endptr, 0);
    if (errno != 0 || *endptr != '\0' || seed > UINT_MAX) {
        fprintf(stderr, "%s: invalid seed\n", argv[0]);
        return EXIT_FAILURE;
    }
    srandom((unsigned int) seed);

    while (1) {
        int i;
        long int randomnum = random();
        for (i = 0; i < sizeof randomnum; i++) {
            if (putchar((randomnum >> (i * CHAR_BIT)) & UCHAR_MAX) == EOF) {
                return EXIT_SUCCESS;
            }
        }
    }
}

这是一个程序，而不是设备文件，但其输出格式与您从/dev/urandom 获得的格式相同.您可以将其输出通过管道传递到 dd ，并省略 if .

This is a program, not a device file, but its output is the same format as you'd get from /dev/urandom. You can pipe the output from it into dd and omit if.

如果您需要提供一个真正随机的种子来提供给程序，您可以像这样从/dev/urandom 中获得bash的一个:

If you need to come up with a truly random seed to supply to the program, you can get one in bash from /dev/urandom like this:

seed=$(od -vAn -N4 -tu4 </dev/urandom)

用您计算机上的任何 sizeof(unsigned int)替换4(可能是4).

Replace 4 with whatever sizeof(unsigned int) is on your machine (it's probably 4).

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