For anybody interested, the configuration of the TlsVersions DWORD in the registry is more granular than the KB article lets on as you actually get control of both the client and server version behaviour, it is not lumped together. The values map to the SP_PROT flags defined in schannel.h, documented online as part of the SCHANNEL_CRED structure under grbitEnabledProtocols. http://msdn.microsoft.com/en-gb/library/windows/desktop/aa379810.aspx SP_PROT_TLS1_SERVER 0x00000040 SP_PROT_TLS1_CLIENT 0x00000080 SP_PROT_TLS1_1_SERVER 0x00000100 SP_PROT_TLS1_1_CLIENT 0x00000200 SP_PROT_TLS1_2_SERVER 0x00000400 SP_PROT_TLS1_2_CLIENT 0x00000800 For standards compliant TLS implementations, you just need an intersection of protocol support between client and server. I am definitely curious if anybody encounters a buggy SSL/TLS library in use in the wild that rejects a TLS 1.1 or 1.2 Client Hello... Nick