🚀 go-pugleaf

    Why not just go buy an HP-48 and replace the chip with your own chip
    that has everything you want.  C'mon you need to watch more 007
    movies ...

Because only techno geeks carry around HP-48's and techno geeks are
automatically suspicious characters.  Also, if by "replace the chip"
you mean "replace the processor", it means you are carrying around
a modified calculator, which is *really* suspicious.  If you just
program the encryption into the HP48, that means you're carrying
around an HP48 with a crypto program, which is incriminating if
they've captured a similar unit from another spy. 

You want to use an unmodified, non-fancy, non-techno-geek, consumer
calculator identical to those used by millions of innocent people.