A method of verifying a speech input can include determining pronunciation data for a received user spoken utterance specifying a word and speech recognizing further user spoken utterances specifying individual characters of the word. An N-best list can be generated for each received user spoken utterance specifying a character. A grammar can be automatically generated that includes word candidates using the N-best list for each user spoken utterance specifying a character. Pronunciation data for each word in the grammar can be generated automatically. The pronunciation data from the user spoken utterance specifying the word can be compared with pronunciation data for the word candidates of the grammar to determine at least one match.