Normally, encryption is done with static key sizes e.g. 1024 bit, 2048 bit, 4096 bit, etc. We only use keys with the length of secure prime numbers, e.g. 5717 bits. One of our research projects has shown that encryption keys are particularly difficult to break when they have the lengths of prime numbers. Big bruteforce key-hacking clusters cannot be optimized for such modified key sizes. Our VPN gateways use dynamically generated keys of prime number length between 5000 and 8000 bits. For a bruteforce cluster to hack such a key, it must determine the new key size after each key exchange, then adapt to this size and then has a maximum of 24 hours to compute the newly generated key.