Strange behavior in crypto random routines

[0ne-bey0nd]

the code

#include "ENCRYPTO_utils/constants.h"
#include "ENCRYPTO_utils/typedefs.h"
#include <ENCRYPTO_utils/crypto/crypto.h>
#include <cstdint>
#include <iostream>
void print_bytes(uint8_t *bytes, uint32_t num_bytes) {
    for (uint32_t i = 0; i < num_bytes; i++) {
        std::cout << (int)bytes[i] << " ";
    }
    std::cout << std::endl;
}

#define RANDOM_BYTES_NUM 16

int main() {
    uint8_t random_bytes[RANDOM_BYTES_NUM];
    uint8_t seed = 42;
    seclvl secure_level = ST;

    uint32_t random_bytes_num = RANDOM_BYTES_NUM;
    crypto crypto_obj(secure_level.symbits, &seed);

    crypto_obj.gen_rnd(random_bytes, random_bytes_num);
    print_bytes(random_bytes, random_bytes_num);

    std::cout << "seed: " << (int)seed << std::endl;
    std ::cout << "random_bytes_num: " << random_bytes_num << std::endl;

    crypto_obj.gen_rnd_from_seed(random_bytes, random_bytes_num, &seed);
    print_bytes(random_bytes, random_bytes_num);
}

Output

152 227 184 124 228 237 196 24 218 98 124 189 49 97 171 171 
seed: 42
random_bytes_num: 16
152 227 184 124 228 237 196 24 218 98 124 189 49 97 171 171 

Now I just exchange the sequence of these two lines like :

    uint32_t random_bytes_num = RANDOM_BYTES_NUM;
    crypto crypto_obj(secure_level.symbits, &seed);

to

    uint32_t random_bytes_num = RANDOM_BYTES_NUM;
    crypto crypto_obj(secure_level.symbits, &seed);

so the code is

#include "ENCRYPTO_utils/constants.h"
#include "ENCRYPTO_utils/typedefs.h"
#include <ENCRYPTO_utils/crypto/crypto.h>
#include <cstdint>
#include <iostream>
void print_bytes(uint8_t *bytes, uint32_t num_bytes) {
    for (uint32_t i = 0; i < num_bytes; i++) {
        std::cout << (int)bytes[i] << " ";
    }
    std::cout << std::endl;
}

#define RANDOM_BYTES_NUM 16

int main() {
    uint8_t random_bytes[RANDOM_BYTES_NUM];
    uint8_t seed = 42;
    seclvl secure_level = ST;

    crypto crypto_obj(secure_level.symbits, &seed);
    uint32_t random_bytes_num = RANDOM_BYTES_NUM;
    crypto_obj.gen_rnd(random_bytes, random_bytes_num);
    print_bytes(random_bytes, random_bytes_num);

    std::cout << "seed: " << (int)seed << std::endl;
    std ::cout << "random_bytes_num: " << random_bytes_num << std::endl;

    crypto_obj.gen_rnd_from_seed(random_bytes, random_bytes_num, &seed);
    print_bytes(random_bytes, random_bytes_num);
}

now the strange things have happened, the output turns to

236 115 137 45 80 65 119 233 123 140 77 2 95 172 158 251 
seed: 42
random_bytes_num: 16
152 227 184 124 228 237 196 24 218 98 124 189 49 97 171 171

It does confuse me and I need help 🙂