  In Proc Math Sci 129, 70(219), Rakesh Pawar considers and solves a certain
extension problem. In this note, we observe that the existence and uniqueness
of differential characters (defined as objects which fit into a hexagon
diagram) follow directly from Rakesh Pawar's results. This provides an
alternate proof of a weaker version of the results of J. Simons and D.
Sullivan, Journal of Topology, 2008, vol 1:45-56. Further this approach
directly shows that the hexagon diagram uniquely determines the differential
K-theory groups upto an isomorphism.
