There is QR code provider and QR code scanner. QR code provider includes Naver (Google in South Korea) and Kakao (WhatsApp in South Korea). QR code scanner is mandatory at venues. QR code is a random UUID. Venues keep UUID (but do not know real world identity), providers keep UUID-to-identity mapping (but do not know real world activity), KCDC gets feed from both venues and providers, join them, and do the contact tracing. In particular, it is legally mandated that only KCDC can do the join.
There is QR code provider and QR code scanner. QR code provider includes Naver (Google in South Korea) and Kakao (WhatsApp in South Korea). QR code scanner is mandatory at venues. QR code is a random UUID. Venues keep UUID (but do not know real world identity), providers keep UUID-to-identity mapping (but do not know real world activity), KCDC gets feed from both venues and providers, join them, and do the contact tracing. In particular, it is legally mandated that only KCDC can do the join.