Resource Nullifier

A resource nullifier is a computed field, the publishing of which consumes the associated with the nullifier resource. For a resource \(r\), the nullifier is computed from the resource's plaintext and a key called a nullifier key: \(r.nf = h_{nf}(nk, r)\). A resource can be consumed only once. Nullifiers of consumed resources are stored in a public add-only structure called the resource nullifier set (\(NFset\)). This structure is external to the resource machine, but the resource machine can read from it.

Every time a resource is consumed, it has to be checked that the resource existed before (the resource's commitment is in the \(CMtree\)) and has not been consumed yet (the resource's nullifier is not in the \(NFset\)).

The nullifier set must support the following functionality:

• WRITE(nf) adds an element to the nullifier set.
• EXISTS(nf) checks if the element is present in the set, returning a boolean.