Windows generate random bytes to uint64_t

genRandom.c

// generate random unsigned 64bit integer


#ifdef _WIN32
  #define __alignof__ __alignof
  #define snprintf(buf, bufSize, format, arg) _snprintf_s(buf, bufSize, _TRUNCATE, format, arg)
  #define strtoll _strtoi64
  #define strtoull _strtoui64
  #define PRId64 "lld"
  #define PRIu64 "llu"
  #include <windows.h>
  #pragma comment(lib, "advapi32.lib")
  #include <Wincrypt.h>
#endif


uint64_t crypto_generate_rand() {

    bool result = false;
    HCRYPTPROV prov = 0;
    BYTE pbBuffer[8] = {0};
    DWORD dwLength;
    uint64_t randval = 0;

    if (!CryptAcquireContext(&prov, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
        return randval;
    }
    
    if (!CryptGenRandom(prov, dwLength, pbBuffer)) {
        if (!CryptReleaseContext(prov, 0)) {
            printf("Unable to release context\n");
            return randval;
        }
        printf("Released crypto context\n");
        return randval;
    }
    
    if (!CryptReleaseContext(prov, 0)) {
        printf("Unable to release context\n");
        return randval;
    }
    
    randval = *(uint64_t *)pbBuffer;
    return randval;
};

int main () {
  
  uint64_t rand = crypto_gen_rand();
  printf("%\n" PRId64, rand);
}