Currently Ethereum uses modified Merkle patricia trie and maybe plan to move to a sparse Merkle tree (SMT), which both support `proof of non-inclusion', i.e. allowing one to proof that some key does not stored in the data structure. Simple Merkle trees lack that feature. My question is why is this feature needed in Ethereum?

1 Answer 1


In some variations of plasma you need to prove that you didn't spend your balance.

For example if you want to exit a instance of plasma.

  • I don't know plasma, can you provide a reference / elaborate more on this please?
    – Bush
    Commented Nov 8, 2019 at 14:53
  • @Bush Plasma is a proposal for scalability for Eth 1.0 ethresear.ch/t/minimal-viable-plasma/426, one of the variations proposed is Plasma Cash that uses sparse merkle trees ethresear.ch/t/…
    – Ismael
    Commented Nov 8, 2019 at 17:02

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