What is the best replacement for windows rand_s on Linux / POSIX?

Question

The problem is not in chance itself (we have rand), but in cryptographically secure PRNG. What can be used on Linux or ideally POSIX? Does NSS have anything useful?

Clarification . I know about / dev / random, but may end in an entropy pool. And I'm not sure if the cryptographic security of / dev / urandom is guaranteed.

Answer 1

Use /dev/random(requires user input, such as mouse movement) or /dev/urandom. The latter has an entropy pool and does not require any user input if the pool is empty.

You can read from the pool as follows:

char buf[100];
FILE *fp;
if (fp = fopen("/dev/urandom", "r")) {
    fread(&buf, sizeof(char), 100, fp);
    fclose(fp);
}

Or something like that.

Answer 2

Wikipedia ( ):

/dev/random /dev/urandom ( "" ), . , , , /dev/random. , . .

Answer 3

The device /dev/randommust be a source of cryptographically secure bits.