Patent ID: 8744850

Claim:
A method implemented by a computing system for selecting challenge items to discriminate between humans and machines in determining access to data and/or resources of a target computing system, comprising: (a) providing data identifying a first set of diphones to be assessed by the computing system, wherein each of said first set of diphones represents a sound associated with an articulation of a pair of phonemes in a natural language; (b) generating a plurality of articulation scores using the computing system based on measuring acoustical characteristics of a reference machine text to speech (TTS) system articulation of each of said first set of diphones; and (c) selecting challenge text including words and phrases from the natural language using the computing system based on said plurality of articulation scores; wherein said challenge text has machine-indicative acoustical characteristics detectable by a speech processing computing system when articulated by the reference machine TTS system or another machine TTS system such that said challenge text is useable by an utterance-based challenge system for discriminating between humans and machines.