last weekend we visited freiburg in germany, to attend a concert by reinhard mey. the concert took part in a huge exhibition hall. seating around 4140 persons according to the hall’s homepage, it was one of the hugest concerts i’ve been at (excluding concerts in stadiums where everyone was standing). since reinhard mey plays all by himself – only he, his guitar and his voice –, there wasn’t that much to see from where we were seated (and that was still far from the back of the hall). but then, the music counts. and the music was great!

on the next day, we explored freiburg. freiburg is quite beautiful and mostly pedestrian friendly, even though it’s currently crowded with construction sites. (most important consequence is that the trams cannot go to the old city center anymore.) later, we travelled to the schauinslandbahn, a gondola tramway going up a mountain called schauinsland by over 700 meters to a total elevation of 1284 meters. we had a quite beautiful view from there! too bad i didn’t bring any good camera with me… (the fairphone‘s camera isn’t precisely good… even a bit worse than an iphone4 camera. but well, i didn’t buy it for its camera :) )

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.

yesterday, i paid konstanz a short visit. here are some impressions:

last friday, i was visiting stuttgart’s wilhelma. here are some photos, taken before my camera died:

well, last friday i was visiting stuttgart’s wilhelma with a friend of mine, when after some time, my camera (a nikon d40x) stopped working, only displaying “error: press shutter release button again”. after trying a lot of things and searching the web, and finally contacting the support, it looks like i have to send the camera in for repair. so right now i’ll be without a camera for some time… :-(

last week, i was in the black forest for three days, staying in a wonderful and quiet place called maierhof.

monday.

i travelled by train to oppenau, where i was collected by car. here’s a view from the station in oppenau:

on the first evening i did a small tour. after a very short time i met a cat sitting on a bench:

here are some impressions from the trip:

tuesday.

on tuesday, i planned to visit the all saints waterfalls. i first did a longer walk:

then, i got there:

the waterfalls remind me a bit of the sundance canyon which i visited last year:

finally, a view on the all saints’ abbey:

wednesday.

on wednesday, i went on a trip to oppenau:

there, i got a piece of strawberry cake with hot chocolate:

on the way back, i found a really beautiful place:

the second-last photo shows the maierhof. later, in the evening, i went on a second trip, and found this view in a forest:

yesterday, i attended a concert of die toten hosen, a german punk band. the opening band was something from norwegen, and i didn’t really like it. but, opposed to that, the concert by the hosen was good, even though i didn’t knew most of the newer songs. they played a lot of classics, like alles aus liebe, bonny & clyde, eisgekühlter bommerlunder, liebesspieler, schön sein, pushed again, wünsch dir was, zehn kleine jägermeister and hier kommt alex.
the technical gadgets were pretty nice. every band member (except the drummer) had his personal light man, who operated a spotlight aimed on that person. moreover, a set of led arrays hang down above the stage, forming a “broken” monitor, sometimes showing the waveform of the music, or animations fitting to the music.
we got three encores (most of the classic songs were played in the encores), one of them featuring a side blow to berlin, saying that now they’ll play real “jazz” (pronounced as jatz in german), featuring the beginning of eisgekühlter bommerlunder while mimicing jazz.
actually, the concert also had two bad sides. first, as so often, there were some assholes who thought that the smoking ban does not affects them. unfortunately, a common problem :(
the second thing was the great connection of the sap arena to public transportion. there’s a train station very near, the mannheim rangierbahnhof. featuring two wooden (!) platforms and no (!) ticket machine, a huge crowd was squeezed into short fast trains. well, even if there would have been a ticket machine inside the trains (which apparently wasn’t, as it turned out later), it was by no mean possible to reach it. whatever. we were pretty happy as after maybe half an hour the train emptied considerably, allowing us to finally sit down.