This case-insensitive code system http://smart.who.int/trust/CodeSystem/KeyUsage defines the following codes:
Code
Display
Definition
SCA
Signer Certificate Authority (SCA)
A certificate which acts a trust anchor in the verification of the certificate chain for the DSCs issued by a Trust Network participant
DSC
Document Signing Certificate (DSC)
A certificate which may be used to verify a digital signature within a Verfifiable Digital Health Certificate
DECA
Data Exchange Certificate Authority (DECA)
A certificate which acts a trust anchor in the verification of the certificate chain for the DESCs issued by a Trust Network Participant
DESC
Data Exchange Signing Certificate (DESC)
A certificate which may be used to initiate a secure data exchange connection (e.g. mTLS) between Trust Network Participants
TLS
Transport Layer Security (TLS)
Used for establishing (m)TLS connections with systems, in particular between the Trust Network Gateway and backend systems of a Trust Network Participant
UP
Upload (UP)
Used to verify digital signature of cryptographically signed content uploaded to services within the Global Digital Health Certification Network, in particular the Trust Network Gateway