today i was in bad säckingen to give a talk at the kinderuni (children university) hochrhein, a eu-funded joint project between the two cities bad säckingen in germany and stein (ag) in switzerland. in the talk, i tried to explain kids, age 8 to 12, a bit about cryptography.
starting with caesar-type ciphers and more general substitution ciphers, i then continued to explained how to crack such ciphers using frequency analysis. this included a live demonstration, which was quite fun thanks to all the contributions from the audience. after shortly giving hints on how to improve on ciphers, i quickly presented the advanced encryption standard before continuing with the second part of the presentation: public key cryptography.
i began by explaining the situation: two cats want to communicate / exchange something (like cat food :-) ), while a third cat is watching / able to intercept (eat). after mentioning diffie and hellman, i continued with a more practical example: a simple massey-omura three-pass protocol type exchange using a box and two padlocks. this was another great thing, asking the kids how they think this could work after presenting the box and the padlocks. and the sudden murmur of understanding when the second lock got added to the box and the box was sent back.
afterwards i asked the kids how they think this system could be attacked, and they both came up with the bruteforce (crack the box open) and the more tricky (man-in-the-middle attack) variant. great!
the last slides on factoring-based crypto and elliptic curves were quite hard to comprehend, as i knew beforehand, but at least they now know that there’s more out there for which they have to learn more about mathematics :-)
if you’re interested, you can download the slides here.