7.4. Data Origin Authentication Considerations

7.4. Data Origin Authentication Considerations

Note that in pair-wise communications, integrity and data origin authentication are provided together. However, in group scenarios where the keys are shared between members, the MAC tag only proves that a member of the group sent the packet, but does not prevent against a member impersonating another. Data origin authentication (DOA) for multicast and group RTP sessions is a hard problem that needs a solution; while some promising proposals are being investigated [PCST1] [PCST2], more work is needed to rigorously specify these technologies. Thus SRTP data origin authentication in groups is for further study.

DOA can be done otherwise using signatures. However, this has high impact in terms of bandwidth and processing time, therefore we do not offer this form of authentication in the pre-defined packet-integrity transform.

The presence of mixers and translators does not allow data origin authentication in case the RTP payload and/or the RTP header are manipulated. Note that these types of middle entities also disrupt end-to-end confidentiality (as the IV formation depends e.g., on the RTP header preservation). A certain trust model may choose to trust the mixers/translators to decrypt/re-encrypt the media (this would imply breaking the end-to-end security, with related security implications).