Verify the ledger

Every trade, dividend and adjustment is an entry in an append-only ledger. The database refuses to change or delete an entry; a correction is a new entry that points at the old one.

Each entry is written in a fixed text form (keys sorted, no spaces, amounts in paise as whole numbers) and hashed with SHA-256. The text includes the previous entry's hash, so changing any entry changes every hash after it.

After each trading day the engine commits that day's entries and the last hash (the anchor) to the public git repository. Git records when each anchor was committed, so rewriting the ledger would mean rewriting public git history.