7.6.4 Participant Join (Leader)

Given a leader ` and a participant i joining meeting meetingID on hardwareID, the leader:

1. Fetches IVKi from the key server.

2. Fetches Sigi and pki from the meeting’s “bulletin board.”

3. Computes Bindingi ← (meetingIDkmeetingUUIDkikhardwareIDkIVKikpki ).

4. Defines Contextsign ← "Zoombase-1-ClientOnly-Sig-EncryptionKeyAnnouncement".

5. Verifies the signature: Sign.Verify(IVKi , Sigi , Contextsign, Bindingi ).

6. If verification fails, it aborts.

7. Computes Meta ← (meetingIDkmeetingUUIDk`ki).

8. Defines ContextKDF ← "Zoombase-1-ClientOnly-KDF-KeyMeetingSeed".

9. Defines Contextcipher ← "Zoombase-1-ClientOnly-Sig-EncryptionKeyMeetingSeed".

10. Computes C ← Box.Enc(sk` , pki , ContextKDF, Contextcipher, Meta,(MK, mkSeqNum)).

11. Posts (i, C) to the “bulletin board.”