The asymmetric encryption system is state of the art and we use the highest level of AES with 256bit key exchange and a RSA key length of 2048bit.
The STU-541 offers TLS (transfer layer security) encryption. TLS uses certificated public key cryptography to encrypt (or otherwise agree) a short random or random-like message. This short message, now known only to the two communicating parties, is then used to generate key material for much faster encryption and authentication algorithms of a mutually agreed cipher suite which are used to protect the communication session.