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A Simulation of Semaphores

The last couple of weeks, or even months, have been rather busy. First of all it’s busy at work, but it doesn’t stop there of course. I start my day by preparing breakfast and lunch packages for the whole family and bringing my daughter to kindergarten. Luckily I don’t have to drive that far to work and I don’t have to sit in the daily traffic jams heading towards the big cities unless I need to go somewhere.

When I come home, I need to pick up my 5 year old son, prepare dinner, eat of course, wash up the dishes – since our Italian design dish washer is broken and the repair man seems to have a long waiting list – put the kids in the bath and then in their beds. Meanwhile I try to write a couple of sentences of a SDN web log or article. In fact I’m currently writing these sentences with my 22 month old daughter on my lap while she wants to type her own stuff, use the mouse, grab everything and throw it away (and wants it back). For the record, my wife and I share household work. Most things we do together, or one does what he/she is best in, whether he/she likes it or not.

Once the kids are in bed I try to catch up on the news, watch a documentary or a movie, or in extremis one of the countless brainless reality shows on TV, read a book and complete the SDN stuff that I started. That is if I don’t have a course, an SDN meets Labs at Walldorf or the SDN event in Brussels (I’m doing a presentation), because that means that I need to catch up on my mail and even do some work at home via our VPN. It doesn’t stop in the weekend when I have to take my son to judo and swimming lessons as well as doing some shopping at the grocery store. Afternoons are then reserved for mowing the lawn, building a wooden garden seat for the wife or playground set for the kids, or the regular visit to the parents in law. And if any of the aforementioned doesn’t happen there is always some administration to do such as the annual burden of the tax return or time spent at SDN or doing some ‘[acting |]’ in commercials/film/TV. </p>


Wizards of SDN


I’m not complaining though, far from it. Even if I won the lottery, I wouldn’t change a lot (apart from living a bit more luxuriously); otherwise I would bore myself stiff. The only problem is time. That’s why I admire Thomas Jung and Craig Cmehil a lot. Not only for the quality stuff that they produce, but for the fact that they produce so much of it ! The huge amount of points they make is proof of that. Now I’ve been reflecting on this and wondering how they find the time for this since I presume that they also have a family life and have to juggle multiple activities. I came up with two possible explanations. Since it’s Einstein’s celebration year there’s been a lot of documentaries broadcast concerning his life and work. It wasn’t mentioned in these programmes, but it could be possible that Thomas and Craig have found a practical application of the relativity theory in order stretch time and thus have that extra hour a day for writing a web log. Now I’m not good in that matter, so I couldn’t check whether that might be possible and so I’ve found another more plausible explanation. Whereas the MIT students made an automatic paper writing programme  – the title and description of this web log was generated by it – in order to fool people, I wonder if Thomas and Craig didn’t write a cunning application (I’m sure it must be written in BSP) which, in contrary to the MIT thing, spit out an interesting and intelligent web log based on the few keywords they type in. Maybe, maybe not. Until further proof though I’ll stick to my original idea: they are geniuses. They don’t spend time in lengthy introductions either, as I tend to do (sometimes), that’s for sure.

So what’s the point of the introduction this time? Well I’ve spent 713 words finding excuses for not doing what I promised in my “Mr Spamman, don’t bring me a dream” web log . I said that an in depth article concerning spam, prevention and the honey pot project would follow shortly. After nearly two months, it is still not there. Actually I didn’t even start it. Shame on me. But things crop up and the plans have changed somewhat too. Since there is a saying that an image tells more than 1000 words, I decided to submit a proposal for the one-hour lecture spot for SDN members at TechEd ‘05. So if you like the subject and want to know more on it, don’t hesitate to vote (you need to be logged in) for this subject. </p>


Spam via SDN?


Having said this, I was intrigued by the Giving out e-mail addresses on giving out e-mail addresses and the amount of work it would be for the SDN developer to implement it. I wanted to help, so I started to think about an easy method that the SDN developers only need to copy/paste. In fact I came up with two things.

The first thing is to install a honey pot as described in the earlier mentioned web log. One helps the community by understanding the spam cycle and fighting spammers with all legal methods, which is a solution with long term benefits.

Secondly, a quick win solution which gives protection against standard e-mail harvesting. Let’s assume the following scenario. There is an SDN page where a (couple of) e-mail addresses are given, if someone clicks on an address the mail program should popup in order to mail the person. There are already some precautions one could take:





•  0: the user gets an arithmetic problem to solve. The user supplies an answer that is checked for correctness

•  1: the sum wasn’t correct, so we are led to wonder whether the user really was human, scattered or simply not smart enough (to use a calculator)

•  2: the answer was correct, so we build the URL in order to launch the mailer.

I suppose the code is rather readable with the comments included. Maybe a little elaboration on the javascript.

We only need to call the Wallace function in state 2. The function will call the Go function with a delay of 500 milliseconds, because we need to open the mailto URL first. We presume of course that the user has a mailer installed and configured. The Go function will close the popup. There are some pitfalls with this. First of all, we need to prevent the browser from asking for confirmation when the window is closed. This rather poor security measure can be fooled easily as you will see. Secondly, this will never work standalone in a Firefox browser. Firefox only allows windows to be closed by javascript if the window is opened by javascript. That’s why gromit.htm calls wallace.htm within a popup.




Voila, as you can see, it isn’t difficult to make the harvesters’ life a bit harder. It is easy for the SDN developers (or anybody else) to implement. That’s also my submission for Craig’s Challenge! Are you ready?, if SDN could provide the photo’s;-) Seriously, please submit your entries and astonish the SDN community!

Having said this I wouldn’t – in contrary to Edward Mellodew’s request – apply this to web logs, articles and forum posts. It’s the sole responsibility of the author whether he/she wants to expose e-mail addresses or not. SDN can’t know if an e-mail address needs to be protected or not (e.g. not needed in the code example above) or can be held responsible for users negligence. That reminds me of the urban legend

of an elderly pet owner who accidentally kills her animal companion by attempting to dry it in a microwave oven. The pet obviously didn’t survive the experiment.

As said, this only covers a small part of the possible one-hour lecture at TechEd ‘05. So if you like the subject and want to know more on it, don’t hesitate to vote (you need to be logged in) for this subject</p>

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  • The secret to my weblogs is actually my cat.  You see I was working really late one night and  fell asleep with my laptop on and a weblog still being edited on the screen.  My cat jumped up and decided to snuggle up to the warm glow of the laptop. 

    To my suprise I woke up the next morning and my cat's pracing around on the keyboard of my laptop had actually produced a rather intelligable weblog on the subject of BSP. So my secret is that I sleep while my cat actually writes my best works. 

    Now my cat is pregnant and should have her kittens any day.  I am hoping at least one of the kittens is an expert in ESA.  If you are interested in increasing your SDN content output, you might consider purchasing one of the kittens.  I warn you though, I won't part with them easily.

  • Since I've been living here in Germany and the elves seem to be quite active here. One night I was sitting on the computer working late and had a little snack with me when my (at the time girlfriend) hollared that it was getting late and time for bed. I went since it was really late. The next morning I woke up thinking that it might have been a bad idea to leave the snack laying there, of course then I realized that I was in Germany and not Florida so there's not as many bugs. Much to my surprise the snack was gone and I had posted a weblog on SDN. I tested this the next night with another snack and volia! Now I've given up trying to find who uses my computer at night and spits out the weblogs I just keep leaving milk and cookies 😉