A Master List is a list of CSCA certificates that has itself been produced and digitally signed by an issuing State. In simple terms, a PKD participant may bilaterally exchange CSCA certificates with a number of other States, authenticate the certificates, then assemble a list and sign it with its national Master List signing certificate. This list containing all the CSCAs that the State trusts is called a Master List and can be uploaded to the ICAO PKD. This Master List can then be downloaded from the ICAO PKD by others who trust the country that has issued the Master List and wish to obtain those CSCA certificates.
The publication of a Master List enables other receiving States to obtain a set of CSCA certificates from a single source (the Master List issuer) rather than undertake direct bilateral exchange with each of the Issuing Authorities or organizations represented on that list.