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Certificate infrastructure requirements for Lync Server 2013


Topic Last Modified: 2016-06-23

Lync Server 2013 requires a public key infrastructure (PKI) to support TLS and mutual TLS (MTLS) connections.

Lync Server uses certificates for the following purposes:

  • TLS connections between client and server

  • MTLS connections between servers

  • Federation using automatic DNS discovery of partners

  • Remote user access for instant messaging (IM)

  • External user access to audio/video (A/V) sessions, application sharing, and conferencing

  • Mobile requests using automatic discovery of Web Services

For Lync Server, the following common requirements apply:

  • All server certificates must support server authorization (Server EKU).

  • All server certificates must contain a CRL Distribution Point (CDP).

  • All certificates must be signed using a signing algorithm supported by the operating system. Lync Server 2013 supports the SHA-1 and SHA-2 suite of digest sizes (224, 256, 384 and 512-bit), and meets or exceeds the operating system requirements. For operating system support, see


    Using the RSASSA-PSS signature algorithm is unsupported, and may lead to errors on login and call forwarding issues, among other problems.

  • Auto-enrollment is supported for internal servers running Lync Server.

  • Auto-enrollment is not supported for Lync Server Edge Servers.

  • When you submit a web-based certificate request to a Windows Server 2003 CA, you must submit it from a computer running either Windows Server 2003 with SP2 or Windows XP.

    Note that although KB922706 provides support for resolving issues with enrolling web certificates against a Windows Server 2003 Certificate Services web enrollment, it does not make it possible to use Windows Server 2008, Windows Vista, or Windows 7 to request a certificate from a Windows Server 2003 CA.

  • Encryption key lengths of 1024, 2048, and 4096 are supported. Key lengths of 2048 and greater are recommended.

  • The default digest, or hash signing, algorithm is RSA. The ECDH_P256, ECDH_P384, and ECDH_P521 algorithms are also supported.