For the actual media data transfer between two end points, the RTP (Real-Time-Transport Protocol) has previously been used. Within the encryption scenario, an end point can be a SwyxIt! Classic, SwyxPhone, ConferenceMgr, LinkMgr, Gateway or a device from another manufacturer. With SRTP it is now possible to transfer media data encrypted and authenticated. SRTP is based on RTP and encrypts the data stream with the encryption algorithm AES (Advanced Encryption Standard).

To enable secure communication by SRTP, a common key (the so-called "PreSharedKey" (PSK)), must be defined between SwyxServer and the respective end point.

SwyxServer distributes a key (PSK) to each end point logging on. End point A is given PSK "A" and end point B PSK "B".

For all end points which use the SwyxWare database (e.g. , SwyxIt! Classic, PhoneMgr, ConferenceMgr, LinkMgr, Gateway), SwyxServer automatically creates and distributes a PreSharedKey. On each successful logon of an end point, another key is generated and distributed encrypted to the end point.

Exceptions to the automatic PSK distribution are devices from third party manufacturers. The key is not automatically assigned to these by SwyxServer. In such cases the key must be stored manually in the device (e.g. via a web interface). Furthermore, it must be configured in the properties of the user who uses this device. See also 11.2.1.9 The "Encryption" Tab.

 

The keys for a SwyxLink trunk and a SIP link must also be created manually. For a SwyxLink trunk this must be set correspondingly on both SwyxServer sides; for a SIP link, on the SwyxServer side and on the provider side.

The subsequent exchange of keys by MIKEY and the SRTP connection proceed in exactly the same way for the end points which are given a key manually as for the end points which receive a PSK automatically.

The end point from which the call is outgoing (here end point A) generates a session key (SK). The secure exchange of the session key is ensured by the protocol MIKEY (Multimedia Internet KEYing). This session key is used by SRTP to encrypt the data stream.

The media data is encrypted with SRTP. This means that calls can no longer be listened to or recorded..

Whether a call is established, and whether it is correspondingly encrypted from end point to end point (e. g. from SwyxIt! Classic to SwyxIt! Classic), is ultimately dependent on the encryption settings within the user properties: