有没有一个函数生成一个随机int数在C?或者我必须使用第三方库?
当前回答
如果您需要128个安全随机位,符合RFC 1750的解决方案是读取已知可以生成可用熵位的硬件源(例如旋转磁盘)。更好的是,好的实现应该使用混合函数组合多个源,并最终通过重新映射或删除输出来消除输出分布的倾斜。
如果你需要更多的比特,你需要做的就是从128个安全随机比特的序列开始,并将其拉伸到所需的长度,将其映射到人类可读的文本等等。
如果你想在C中生成一个安全的随机数,我将遵循这里的源代码:
https://wiki.sei.cmu.edu/confluence/display/c/MSC30-C.+Do+not+use+the+rand%28%29+function+for+generating+pseudorandom+numbers
注意,对于Windows bbcryptgenrandom是使用的,而不是CryptGenRandom,在过去的20年里已经变得不安全。您可以亲自确认BCryptGenRandom符合RFC 1750。
For POSIX-compliant operating systems, e.g. Ubuntu (a flavor of Linux), you can simply read from /dev/urandom or /dev/random, which is a file-like interface to a device that generates bits of entropy by combining multiple sources in an RFC 1750 compliant fashion. You can read a desired number of bytes from these "files" with read or fread just like you would any other file, but note that reads from /dev/random will block until a enough new bits of entropy are available, whereas /dev/urandom will not, which can be a security issue. You can get around that by checking the size of the available entropy pool, either my reading from entropy_avail, or by using ioctl.
其他回答
试试这个,我把上面已经提到的一些概念放在一起:
/*
Uses the srand() function to seed the random number generator based on time value,
then returns an integer in the range 1 to max. Call this with random(n) where n is an integer, and you get an integer as a return value.
*/
int random(int max) {
srand((unsigned) time(NULL));
return (rand() % max) + 1;
}
C程序生成9到50之间的随机数
#include <time.h>
#include <stdlib.h>
int main()
{
srand(time(NULL));
int lowerLimit = 10, upperLimit = 50;
int r = lowerLimit + rand() % (upperLimit - lowerLimit);
printf("%d", r);
}
通常我们可以生成一个介于lowerLimit和upperLimit-1之间的随机数
例如,lowerLimit包含或说r∈[lowerLimit, upperLimit)
如果您需要128个安全随机位,符合RFC 1750的解决方案是读取已知可以生成可用熵位的硬件源(例如旋转磁盘)。更好的是,好的实现应该使用混合函数组合多个源,并最终通过重新映射或删除输出来消除输出分布的倾斜。
如果你需要更多的比特,你需要做的就是从128个安全随机比特的序列开始,并将其拉伸到所需的长度,将其映射到人类可读的文本等等。
如果你想在C中生成一个安全的随机数,我将遵循这里的源代码:
https://wiki.sei.cmu.edu/confluence/display/c/MSC30-C.+Do+not+use+the+rand%28%29+function+for+generating+pseudorandom+numbers
注意,对于Windows bbcryptgenrandom是使用的,而不是CryptGenRandom,在过去的20年里已经变得不安全。您可以亲自确认BCryptGenRandom符合RFC 1750。
For POSIX-compliant operating systems, e.g. Ubuntu (a flavor of Linux), you can simply read from /dev/urandom or /dev/random, which is a file-like interface to a device that generates bits of entropy by combining multiple sources in an RFC 1750 compliant fashion. You can read a desired number of bytes from these "files" with read or fread just like you would any other file, but note that reads from /dev/random will block until a enough new bits of entropy are available, whereas /dev/urandom will not, which can be a security issue. You can get around that by checking the size of the available entropy pool, either my reading from entropy_avail, or by using ioctl.
你也可以使用mathgl库#include <mgl2/mgl_cf.h>(虽然首先你需要安装它,我自己通过MSYS2安装)函数mgl_rnd()。它也有均匀分布,高斯分布等等。这是ez的用法。但我不知道它的特点。
注意:为了安全性,不要使用rand()。如果您需要加密安全的号码,请参阅此答案。
#include <time.h>
#include <stdlib.h>
srand(time(NULL)); // Initialization, should only be called once.
int r = rand(); // Returns a pseudo-random integer between 0 and RAND_MAX.
在Linux上,您可能更喜欢使用random和srandom。