1. A method performed by at least one processor executing computer program instructions stored on a non-transitory computer-readable medium, the method comprising: (A) applying a matched filter to: (1) a data vector DV; and (2) a set RV, the set RV containing a plurality of reference vectors, wherein each vector RV[i] in the plurality of reference vectors has index i in the set RV; to produce matched filter output representing a similarity estimate set MSV comprising a plurality of similarity responses corresponding to the plurality of reference vectors in the set RV; wherein each similarity response MSV[i] in the plurality of similarity responses has index i in the similarity estimate set MSV; wherein each said similarity response MSV[i] in the similarity estimate set MSV contains a corresponding measure of similarity representing a strength of a match between the data vector DV and a corresponding reference vector RV[i] in the set RV; (B) applying a first filter to select a peak similarity response PK 1 from the similarity estimate set MSV, the peak similarity response PK 1 representing a reference to a peak element of the similarity estimate set MSV, wherein none of the plurality of similarity responses is greater than a value of the peak element; (C) applying a second filter to the similarity estimate set MSV to derive a second similarity response PK 2 from the similarity estimate set MSV, wherein deriving the second similarity response PK 2 from the similarity estimate set MSV omits the peak element of the similarity estimate set MSV; and (D) applying a confidence estimation output filter to derive, from the peak similarity response PK 1 and the second similarity response PK 2 , confidence estimate output representing a degree of confidence in the correctness of the matched filter output.