The "CTI Client" uses an own compiled version of libSRTP. See "srtp2.dll" in the program directory.

Source of libSRTP:
- https://github.com/ESTOS/libsrtp
- https://github.com/cisco/libsrtp


libSRTP is distributed under the following license, which is included in the source code distribution. 
It is reproduced in the manual in case you got the library from another source.

> Copyright (c) 2001-2017 Cisco Systems, Inc.  All rights reserved.
>
> Redistribution and use in source and binary forms, with or without
> modification, are permitted provided that the following conditions
> are met:
>
> - Redistributions of source code must retain the above copyright
>   notice, this list of conditions and the following disclaimer.
>
> - Redistributions in binary form must reproduce the above copyright
>   notice, this list of conditions and the following disclaimer in
>   the documentation and/or other materials provided with the distribution.
>
> - Neither the name of the Cisco Systems, Inc. nor the names of its
>   contributors may be used to endorse or promote products derived
>   from this software without specific prior written permission.
>
> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
> FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
> COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
> INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
> (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
> SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
> HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
> STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
> ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
> OF THE POSSIBILITY OF SUCH DAMAGE.