7. The method of claim 6 , wherein the step of generating a speech recognition grammar comprises generating for each character of the character string a corresponding pool of distractors that comprises each letter of the pre-selected alphabet that is acoustically dissimilar to the corresponding character.
8. The method of claim 7 , further comprising receiving a speech utterance, wherein the speech utterance comprises a sequential enunciation of letters of the pre-selected alphabet interspersed with pauses between each pair of enunciations, and wherein the target entry is determined based upon the received speech utterance.