Remove "using smartphones" from title

[dbosk]

This scheme is not implemented using a smartphone although
the title of the work contains the words “using smartphones”
and further the benchmark values seem to originate from the old
implementations not belonging to the author/authors. It seems that
this scheme cannot be implemented because of today’s technology
since some restrictions for signing the identity credential by CA,
distance-bounding protocols, etc. on the smartphone exist. It is not
fair to use “using smartphones” in the title even if this will be
considered as future work.