24. A system for speech-based user authentication, comprising: a processor configured to receive a spoken utterance of a speaker, generate a phoneme-independent matrix based on the spoken utterance, wherein the phoneme-independent matrix comprises a plurality of phoneme-independent feature vectors each having been extracted from a respective frame sampled from the spoken utterance at a sampling frequency, decompose the phoneme-independent matrix into multiple sets of vectors at least a first set of vectors defining at least one speaker-specific recognition unit and a second set of vectors defining at least one content reference sequence, compute at least one speaker-specific distribution value based on at least the speaker-specific recognition unit; and authenticate an input speech signal based on the at least one speaker-specific distribution value.
27. The system of claim 24 wherein the processor is further configured to generate the at least one speaker-specific recognition unit from a singular value matrix of a singular value decomposition of the phoneme-independent matrix.