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Encryption for Skype for Business Server 2015

Skype for Business Server 2015
 

Topic Last Modified: 2016-06-06

Skype for Business Server 2015 uses TLS and MTLS to encrypt instant messages. All server-to-server traffic requires MTLS, regardless of whether the traffic is confined to the internal network or crosses the internal network perimeter. When connecting Skype for Business Server 2015 to 3rd party IPPBX systems or SIP trunks TLS is optional but strongly recommended between the Mediation Server and media gateway. If TLS is configured on this link, MTLS is required. Therefore, the gateway must be configured with a certificate from a CA that is trusted by the Mediation Server.

noteNote:
A security advisory regarding SSL 3.0 was published in 2014. Disabling SSL 3.0 in Skype for Business Server 2015 is a supported option. To learn more about the security advisory, see https://blogs.technet.microsoft.com/uclobby/2014/10/22/disabling-ssl-3-0-in-lync-server-2013/.

The following table summarizes the protocol requirements for each type of traffic.

Traffic Protection

Traffic type Protected by

Server-to-server

MTLS

Client-to-server

TLS

Instant messaging and presence

TLS

Audio and video and desktop sharing of media

SRTP

Desktop sharing (signaling)

TLS

Web conferencing

TLS

Meeting content download, address book download, distribution group expansion

HTTPS

Media traffic is encrypted using Secure RTP (SRTP), a profile of Real-Time Transport Protocol (RTP) that provides confidentiality, authentication, and replay attack protection to RTP traffic. In addition, media flowing in both directions between the Mediation Server and its internal next hop is also encrypted using SRTP. Media flowing in both directions between the Mediation Server and a media gateway is optionally encrypted and recommended. The Mediation Server can support encryption to the media gateway, but the gateway must support MTLS and storage of a certificate.

noteNote:
If you are implementing a hybrid environment, you must also modify the Skype for Business Server 2015 encryption level. By default, the encryption level is Required. You must change this setting to Supported by using the Skype for Business Server Management Shell. For more information about setting up hybrid, see Configure hybrid from online to on-premises in Skype for Business Server 2015 in the Deployment documentation.

Skype for Business Server 2015 and Microsoft Exchange Server 2016 operate with support for Federal Information Processing Standard (FIPS) 140-2 algorithms if the Windows Server operating systems are configured to use the FIPS 140-2 algorithms for system cryptography. To implement FIPS support, you must configure each server running Skype for Business Server 2015 to support it.

 
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