A transaction authentication system including a vocabulary database including at least one of a dictionary's words; an utterance database including at least one speaker's utterances; at least one processor in communication with the vocabulary database and the utterance database, the at least one processor programmed or configured to digitally record an utterance from at least one speaker; isolate at least one word of he utterance based on at least one statistical analysis, one acoustic analysis, or any combination thereof; of; match at least one dictionary word from the vocabulary database with at least one word of the utterance in accordance with at least one predefined accuracy criterion; and in response to matching the at least one dictionary word with the at least one word of the utterance, transmit an authentication message.