PERC stands for Privacy Enhanced RTP Conferencing.
PERC is an IETF framework that defines how to maintain E2EE (End-to-End Encryption) in RTP-based conferencing when media passes through middleboxes like SFUs.
The PERC problem
In a standard WebRTC conference using an SFU:
- Media is encrypted with SRTP between each endpoint and the SFU
- The SFU can decrypt and read the media (it needs to access RTP headers for routing)
- True end-to-end encryption is not achieved
PERC defines a double encryption model where:
- An inner encryption layer protects the media content end-to-end (only endpoints can decrypt)
- An outer encryption layer protects the full packet hop-by-hop (the SFU can process headers)
PERC vs Insertable Streams
While PERC was the IETF's approach, browsers implemented E2EE through Insertable Streams instead, which provides a more flexible mechanism for custom encryption at the application level.
