  We describe a new error reconciliation protocol {\it Winnow} based on the
exchange of parity and Hamming's ``syndrome'' for $N-$bit subunits of a large
data set. {\it Winnow} was developed in the context of quantum key distribution
and offers significant advantages and net higher efficiency compared to other
widely used protocols within the quantum cryptography community. A detailed
mathematical analysis of Winnow is presented in the context of practical
implementations of quantum key distribution; in particular, the information
overhead required for secure implementation is one of the most important
criteria in the evaluation of a particular error reconciliation protocol. The
increase in efficiency for Winnow is due largely to the reduction in
authenticated public communication required for its implementation.
