Section 1: Improve description of key derivation

[tuexen]

"Therefore, an SCTP extension that provides a mechanism for deriving shared keys for each association is presented. These association shared keys are derived from endpoint pair shared keys, which are configured and might be empty, and data that is exchanged during the SCTP association setup."

Especially the first sentence appear to me not to rightly capture what is provided. I think some clarification on the shared key properties in general might be needed.

This was reported in Comments on draft-tuexen-tsvwg-rfc4895-bis-04

[tuexen]

Will be done, once key derivation is finalized.