6. Adding SRTP Transforms

6. Adding SRTP Transforms

Section 4 provides examples of the level of detail needed for defining transforms. Whenever a new transform is to be added to SRTP, a companion standard track RFC MUST be written to exactly define how the new transform can be used with SRTP (and SRTCP). Such a companion RFC SHOULD avoid overlap with the SRTP protocol document. Note however, that it MAY be necessary to extend the SRTP or SRTCP cryptographic context definition with new parameters (including fixed or default values), add steps to the packet processing, or even add fields to the SRTP/SRTCP packets. The companion RFC SHALL explain any known issues regarding interactions between the transform and other aspects of SRTP.

Each new transform document SHOULD specify its key attributes, e.g., size of keys (minimum, maximum, recommended), format of keys, recommended/required processing of input keying material, requirements/recommendations on key lifetime, re-keying and key derivation, whether sharing of keys between SRTP and SRTCP is allowed or not, etc.

An added message integrity transform SHOULD define a minimum acceptable key/tag size for SRTCP, equivalent in strength to the minimum values as defined in Section 5.2.