# [sf-lug] Ex 11.7 Exponentiation (understandable) & RSA algorithm (not so!)

jim jim at well.com
Mon Jan 12 08:38:18 PST 2009

```i'd like verification of my understanding of this:
"Let d be the reciprocal of e mod r."

my arithmetic:
if e is 35 and r is 9111,
then d = 1/(35%9111) ## == 1/35 == 0.028571429

On Mon, 2009-01-12 at 00:43 -0800, Asheesh Laroia wrote:
> Alex is going through the _Think Python_ text and it asks about the
> classic RSA cryptography algorithm.
>
> On Fri, 9 Jan 2009, Alex Kleider wrote:
>
> > re ThinkPython, Exercise 11.7:
> >
> > I've made an honest attempt to understand the wiki page referenced, but
> > it's way beyond me. Can you or anyone else suggest a source that might
> > be easier for a non mathematician to understand AND (perhaps more to the
> > point) implement?
>
> It looks like
> http://larrydavidson.blogspot.com/2008/07/teaching-rsa-in-high-school.html
> is useful - what do you think?
>
> > ps if you think this is appropriate for the list, please forward it.
>
> Okay!
>
> -- Asheesh.
>

```