US Patent 10218511 Signature delegation

A signature authority generates a master seed value that is used as the root of a seed tree of subordinate nodes. Each subordinate node of the seed tree is generated from the value of its parent node using a cryptographic hash or one-way function. The signature authority selects subordinate seed values which are distributed to one or more key generators, each of which generates a set of one-time-use cryptographic keys. Each key generator generates a hash tree from its set of one-time-use cryptographic keys, and the root of its hash tree is returned to the signature authority. The signature authority integrates the hashes provided by the key generators into a comprehensive hash tree. The root of the comprehensive hash tree acts as a public key for the signature authority.