CompositeKeyGenerator

A generator for a tree data structure that enables the representation of composite public keys, which are used to represent the signing requirements for multi-signature scenarios. A composite key is a list of leaf keys and their contributing weight, and each leaf can be a conventional single key or a composite key. Keys contribute their weight to the total if they are matched by the signature.

For complex scenarios, such as "Both Alice and Bob need to sign to consume a state S", we can represent the requirement by creating a tree with a root CompositeKey, and Alice and Bob as children. The root node would specify weights for each of its children and a threshold – the minimum total weight required (e.g. the minimum number of child signatures required) to satisfy the tree signature requirement.

Using these constructs we can express e.g. 1 of N (OR) or N of N (AND) signature requirements. By nesting we can create multi-level requirements such as "either the CEO or 3 of 5 of his assistants need to sign".

Composite key implementations will track the minimum total weight required (in the simple case – the minimum number of child signatures required) to satisfy the subtree rooted at this node.