A signature authority generates a master seed value that is used to generate 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 from the seed tree which are distributed to one or more subordinates, each of which generates a set of one-time-use cryptographic keys from the provided seed. Each subordinate generates a hash tree from its set of one-time-use cryptographic keys, and returns the root of its hash tree to the signature authority. The signature authority integrates the hashes provided by the key generators into a comprehensive hash tree, and the root of the hash tree acts as a public key for the signature authority.