rfc8871v8.txt   rfc8871.txt 
skipping to change at line 594 skipping to change at line 594
does accommodate rekeying during the lifetime of a conference. does accommodate rekeying during the lifetime of a conference.
When a Key Distributor decides to rekey a conference, it transmits a When a Key Distributor decides to rekey a conference, it transmits a
new EKTKey message containing the new EKT Key to each of the new EKTKey message containing the new EKT Key to each of the
conference participants. Upon receipt of the new EKT Key, the conference participants. Upon receipt of the new EKT Key, the
endpoint MUST create a new SRTP master key and prepare to send that endpoint MUST create a new SRTP master key and prepare to send that
key inside a FullEKTField using the new EKT Key as per Section 4.5 of key inside a FullEKTField using the new EKT Key as per Section 4.5 of
[RFC8870]. In order to allow time for all endpoints in the [RFC8870]. In order to allow time for all endpoints in the
conference to receive the new keys, the sender should follow the conference to receive the new keys, the sender should follow the
recommendations in Section 4.6 of [RFC8870]. On receiving a new EKT recommendations in Section 4.6 of [RFC8870]. On receiving a new EKT
Key, endpoints MUST be prepared to decrypt EKT tags using the new Key, endpoints MUST be prepared to decrypt EKT Tags using the new
key. The EKT Security Parameter Index (SPI) field is used to key. The EKT Security Parameter Index (SPI) field is used to
differentiate between EKT Tags encrypted with the old and new keys. differentiate between EKT Tags encrypted with the old and new keys.
After rekeying, an endpoint SHOULD retain prior SRTP master keys and After rekeying, an endpoint SHOULD retain prior SRTP master keys and
EKT Keys for a period of time sufficient for the purpose of ensuring EKT Keys for a period of time sufficient for the purpose of ensuring
that it can decrypt late-arriving or out-of-order packets or packets that it can decrypt late-arriving or out-of-order packets or packets
sent by other endpoints that used the prior keys for a period of time sent by other endpoints that used the prior keys for a period of time
after rekeying began. An endpoint MAY retain old keys until the end after rekeying began. An endpoint MAY retain old keys until the end
of the conference. of the conference.
skipping to change at line 791 skipping to change at line 791
EKT Tag data as per [RFC8870]). EKT Tag data as per [RFC8870]).
The KEK is not given to the Media Distributor. The KEK is not given to the Media Distributor.
6.4. Endpoints Fabricate an SRTP Master Key 6.4. Endpoints Fabricate an SRTP Master Key
As stated earlier, the E2E key determined via DTLS-SRTP MAY be As stated earlier, the E2E key determined via DTLS-SRTP MAY be
discarded in favor of a locally generated E2E SRTP master key. While discarded in favor of a locally generated E2E SRTP master key. While
the DTLS-SRTP-derived SRTP master key can be used initially, the the DTLS-SRTP-derived SRTP master key can be used initially, the
endpoint might choose to change the SRTP master key periodically and endpoint might choose to change the SRTP master key periodically and
MUST change the SRTP master key as a result of the EKT key changing. MUST change the SRTP master key as a result of the EKT Key changing.
A locally generated SRTP master key is used along with the master A locally generated SRTP master key is used along with the master
salt transmitted to the endpoint from the Key Distributor via the salt transmitted to the endpoint from the Key Distributor via the
EKTKey message to encrypt media end to end. EKTKey message to encrypt media end to end.
Since the Media Distributor is not involved in E2E functions, it does Since the Media Distributor is not involved in E2E functions, it does
not create this key, nor does it have access to any endpoint's E2E not create this key, nor does it have access to any endpoint's E2E
key. Note, too, that even the Key Distributor is unaware of the key. Note, too, that even the Key Distributor is unaware of the
locally generated E2E keys used by each endpoint. locally generated E2E keys used by each endpoint.
skipping to change at line 1203 skipping to change at line 1203
Initiation Protocol (SIP)", RFC 8224, Initiation Protocol (SIP)", RFC 8224,
DOI 10.17487/RFC8224, February 2018, DOI 10.17487/RFC8224, February 2018,
<https://www.rfc-editor.org/info/rfc8224>. <https://www.rfc-editor.org/info/rfc8224>.
[RFC8827] Rescorla, E., "WebRTC Security Architecture", RFC 8827, [RFC8827] Rescorla, E., "WebRTC Security Architecture", RFC 8827,
DOI 10.17487/RFC8827, January 2021, DOI 10.17487/RFC8827, January 2021,
<https://www.rfc-editor.org/info/rfc8827>. <https://www.rfc-editor.org/info/rfc8827>.
[W3C.CR-webrtc] [W3C.CR-webrtc]
Jennings, C., Boström, H., and J-I. Bruaroey, "WebRTC 1.0: Jennings, C., Boström, H., and J-I. Bruaroey, "WebRTC 1.0:
Real-time Communication Between Browsers", W3C Candidate Real-time Communication Between Browsers", W3C Proposed
Recommendation, <https://www.w3.org/TR/webrtc/>. Recommendation, <https://www.w3.org/TR/webrtc/>.
Acknowledgments Acknowledgments
The authors would like to thank Mo Zanaty, Christian Oien, and The authors would like to thank Mo Zanaty, Christian Oien, and
Richard Barnes for invaluable input on this document. Also, we would Richard Barnes for invaluable input on this document. Also, we would
like to acknowledge Nermeen Ismail for serving on the initial draft like to acknowledge Nermeen Ismail for serving on the initial draft
versions of this document as a coauthor. We would also like to versions of this document as a coauthor. We would also like to
acknowledge John Mattsson, Mats Naslund, and Magnus Westerlund for acknowledge John Mattsson, Mats Naslund, and Magnus Westerlund for
providing some of the text in the document, including much of the providing some of the text in the document, including much of the
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