The definition of the Ledger Layer is NOT part of the specifications of FinP2P - each node and technology vendor may implement it in any way they see fit, as long as the correct behavior of the FinP2P Network Protocol is maintained. This Ledger Layer chapter of this specification is a reference implementation design only.
The FinP2P Core component is stateless and does not save any securities or private information. All securities and private information is stored at the ledger layer, it is separated into two main parts:
Private information relating to users and assets is kept off-chain, and is only shared with other nodes in the FinP2P that are authorized to see that information. This information need to comply with various legal and regulatory requirements such as GDPR, and therefore will not be stored on a DLT platform. While the information itself is not held on chain, we still require the Hash of the data to be kept on the DLT to provide immutability and a method for validating private information provided to other nodes via the FinP2P Network Protocol.
Transaction information for all assets have to be stored on the DLT network chosen by the node, where all information about asset ownership is maintained across a blockchain of multiple financial institutions.