Mint nodes produce mint proofs when issuing ecash, and melt proofs when redeeming (or “burning”) tokens.

A dishonest mint could manipulate these records, falsifying proofs or secretly issuing unbacked ecash, thereby inflating liabilities without users realizing their tokens aren’t properly backed by BTC.

Merkle Sum Sparse Merkle Trees (MSSMTs) offer a cryptographic way to record mint and melt events transparently. They let users verify inclusion of transactions and ensure the mint's liabilities are fully accounted for.

The sum property aggregates token values (minted and burned), while the sparse structure keeps things efficient, even with few transactions