__crypt_tobase64
crypt_private void __crypt_tobase64(char *, uint32_t, int);
__crypt_tobase64(&salt[n], arc4random(), 4);
__crypt_tobase64(&salt[n + 4], arc4random(), 4);
__crypt_tobase64(&salt[n + 8], arc4random(), 4);
__crypt_tobase64(&salt[n + 12], arc4random(), 4);