Ledger Object IDs
Each object in a ledger's state data has a unique ID. The ID is derived by hashing important contents of the object, along with a namespace identifier . The ledger object type determines which namespace identifier to use and which contents to include in the hash. This ensures every ID is unique. To calculate the hash, rippled uses SHA-512 and then truncates the result to the first 256 bits. This algorithm, informally called SHA-512Half, provides an output that has comparable security to SHA-256, but runs faster on 64-bit processors.
Generally, a ledger object's ID is returned as the index field in JSON, at the same level as the object's contents. In transaction metadata, the ledger object's ID in JSON is LedgerIndex.
Tip: The index or LedgerIndex field of an object in the ledger is the ledger object ID. This is not the same as a ledger index.
