[r00t]

the standard gcc library definition for rand() is a simple linear congruential generator

static unsigned long int next = 1;

int rand(void) // RAND_MAX assumed to be 32767
{
    next = next * 1103515245 + 12345;
    return (unsigned int)(next/65536) % 32768;
}

void srand(unsigned int seed)
{
    next = seed;
}

Linear congruential generator should also not be used for cryptographic applications; see cryptographically secure pseudo-random number generator for more suitable generators. If a linear congruential generator is seeded with a character and then iterated once, the result is a simple classical cipher called an affine cipher; this cipher is easily broken by standard frequency analysis.

if you think the embedded devices like your router or printer et al. is using anything fancier you are sadly mistaken

these are your x.509 certificates we're talking about here people