Abstract: Secure site-to-site transactional communication between at least two network servers coupled to a data communication network, including secure registration by an authentication server associated with a multi-site user authentication system. A network server receives a request via a browser f of a client computer. In response, the network server initiates a transaction with the authentication server and defines a data structure, such as a query string, associated with the transaction. The network server also generates a digital signature of the data structure and then adds it to the data structure before directing the client computer from the network server to the authentication server with the data structure and the added digital signature. The network server also adds an index to the data structure. The index is associated with the transaction and unique, per transaction, to the network server initiating the transaction.

Abstract: An “audio challenger” operates by first defining a library of a finite number of discrete audio objects including spoken sounds, such as, for example, individual digits, letters, numbers, words, etc., or combinations of two or more digits, letters, numbers, or words. The spoken sounds are either automatically generated by a computer, or recorded from one or more actual spoken voices. Given this library of audio objects, the audio challenger automatically selects one or more audio objects from the library and concatenates the objects into an audio string that is then automatically processed to add one or more distortions to create a “challenge string.” The distorted challenge string is then presented to an unknown party for identification. If the unknown party correctly identifies the challenge string, then the unknown party is deemed to be a human operator. Otherwise, the unknown party is deemed to be another computer.