2007 Music reviews
Dec 31st 2007
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Second Life Multilanguage support
Sep 11th 2007
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When you are flying around in Second Life you have certainly noticed that there are no support for multi-language, meaning everything is in English and there is no option to change it. The following tutorial will explain how by using textures and the Linden Scripting Language it is possible to make a multi-language support for your world including an adaptive language change for dialog boxes. More > |
Ipod Nano 3g Full Review
Sep 11th 2007
As you may have now seen, the new Nano 3 G was released a few weeks ago. The reviews on the internet concerning the iPod are sometime biased by enthousiastic geeks or early adopters. The following review is 100% objective |
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The new iPod is about 7 cm high and 5.2 cm wide. It’s weight: only 49.2 grams! Although the screen is pretty small it’s a pleasure to watch TV shows or video clips on it. There is no visual difficulty concerning the usage of menus. But for someone who has big thumbs the usage of the click wheel might be adventurous: you will never know if you are going to select the next/previous track or going to change the volume. I would say the click wheel is very sensitive. More > |
Présidentielles 2007 – Professions de foi en version allemande
May 1st 2007
En Alsace-Moselle nous obtenons avec nos affiches/programmes des différents candidats, une version des professions de foi en Allemand. Certaines font un peu sourire 😉
N.B: Gérard Schivardi, Olivier Besancenot et Frédéric Nihous n’ont pas de programmes traduits en Allemand. Vous pouvez cliquer sur les images pour les agrandir.
La version allemande des professions de foi des candidats à l’élection présidentielle 2007) More >
My Sonic Shoes (April 2007) / Contest
Apr 9th 2007
Aim of this contest that was launched to celebrate the release of the Wii Game “Sonic & the Secret Rings” was to put the Sonic shoes in an original picture.
I thought placing Sonic’s shoes on Paris Hilton was funny enough to let this picture compete in this contest 🙂
RSA Diffie-Hellman explained in 3 minutes
Apr 1st 2007
Cryptosystems explained
I was always upset to see that cryptography was made so difficult because so many cryptical maths signs were used.
I wrote this tiny article to easily explain how RSA and Diffie Hellman key exchange are working. This article is not targeted on mathematics fans so they won’t find something new here;-) I hope it can help you to start in the cryptosystem field.
Modulo calculation
The first thing to know in cryptography, is how to handle with modulo calculations. Modulo, what ? No fear it’s very easy to understand.
Just take this example : when a friend of you is telling : “I’ll be back home in 32 hours” how are you converting this in days ?
32 hours = 24 hours + 8 hours
This is equivalent to write : 32 = 24×1 + 8 . Unconsciously you made : 32 divided by 24 and the remainder is 8
So if we turn this in a mathematical way you can write : 32 mod 24 = 8
Another example : If you say “I have a train in 125 minutes“. How are you proceeding to know how many hour(s) and minutes you have to wait ? Very easy : you are going to divide 125 by 60 and then 5 will remain. You have two “full” hours and 5 minutes :
125 = 60×2 + 5 . You can also write : 125 mod 60 = 5
Here is another example : 125 mod 32 = 29. Why ? because 125 = 32 x 3 + 29
Just think about “doing 3 packets of 32 starting at 125 ” and if the remainder is not 0, the number remaining (the red one) will be the solution of your equation.
24 mod 12 = 0 because we have a remainder that equals 0 => 24 = 2 x 12 + 0
Prime numbers
Many properties in cryptography are based on multiplication and factorization of prime numbers. A primer number is a whole number (integer) that can only be divided evenly by itself.
e.g. 2, 3, 5, 7,11,13,17,19,23,27 are prime numbers
24 is not a prime number because it can be divided by 2,3,4,8,12
Generating big prime numbers enables us to have a higher security because they are very hard to find ( due to the property of being divisible by itself). Make the test by yourself : find a prime number higher than 2000. You will need a few seconds to verify the divisors so do computers for very huge prime numbers.
If you are interested, here is a page listing the 1000 first prime numbers : http://primes.utm.edu/lists/small/1000.txt
The Diffie-Hellman key exchange
It’s always a problem when you want to share a key to another person, because you can’t be sure that the “line” or transmission mode is sure enough. That’s why Diffie-Hellman key exchange algorithm was created. The following picture explains the whole process :
RSA
The acronym RSA stands for Ron Rivest, Adi Shamir and Leon Adleman, the three “inventor” of this system. It was in 1977.
RSA is very easy to understand. We will have two persons (say Alice and Bob). They want to communicate together but don’t want to be listened by someone else. So Alice will need to encrypt her message and Bob to decrypt it.
We will first choose two prime numbers p and q so that p and q have no common divider. In other words the greatest common divider of p and q is 1.
Finding p and q
Let’s take as an example p = 7 and q = 3. It’s clear that gcd(7,3) = 1
Now we are going to find n. n equals p x q . So in our example we will have :
n = p x q = 7 x 3 = 21
Alice also needs to compute her private (or so called secret) key and the public key. Bob will also have a private key. With his secret/private key and Alice’s public key Bob will be able to decipher Alice’s message.
In order to compute both keys we need to find e and d so that: e x d mod phi(n) = 1.
Don’t panic 😉
phi(n) = (p-1)(q-1) = (7-1)(3-1) = 12
Now we must find e so that e has no common factor with phi(n). We can also say that gcd(e,phi(n)) = 1 or gcd(e,12).
Let’s take e = 7 ( a quick check gives uses gcd(7, 12) = 1 ) for the sake of showing how the process works.
Now we need to find out d . Finding d is perhaps the most tricky thing of the whole RSA algorithm.
We can write this : 7 d mod 12. To solve this we simply write :
12 = 7 x 1 + 5 (then we pull down the numbers 5 and 2 )
7 = 5 x 1 + 2
5 = 2 x 2 + 1 => Stop !
Extended Euclidean Algorithm
When you have a 1 on the most right side of your equation you stop ! What we just did is called “Extended Euclidean algorithm”. “Funny” name, but easy to solve 😉 Now that we have the number 1 on the right side we can “invert” our equation by writing :
1 = 5 – 2 x 2
and then you will replace by 2 by 7 = 5 x 1 + 2
1 = 5 – ( 7 – 5 x 1) x 2
1 = 5 x 3 – 2 x 7
and now we will replace 5 by 5 = 12 – 7 x 1
1 = (12 – 7 x 1) x 3 – 2 x 7
and by replacing 2 by 5 = 12 – 7 x 1
If we group the 7s and the 12s we have :
1 = 12 x 3 – 5 x 7
What we in fact were trying to reach is a result with following form 1 = 12 x A – 5 x B with A and B unknown. These two unknown numbers are in maths called Bezout coefficients.
Don’t forget that we are working in the ensemble Z12. We can “erase” 3 x 12 because we already have seen that 3 x 12 = 36 and 36 mod 12 = 0
Now we are going to watch the 5 x 7 part. we see the number 5 coming from e . But we want d !
we can now write in this form : -5 + 12 = 7 . This is called the inverse of -5 mod 12. So inverse of -5 mod 12 = 7
and d is going to be : 7 + 12 because we have in our equation mod 12
this gives d = 19.
What happens next if instead of -5 we had a positive number such as 3 ? You would have calculated : d = 3 + 12 = 15
We can now check our result : e x d = 7 x 19 = 133 . And if we decompose 133 we have : 133 = 12 x 11 + 1 The remainder is 1, our calculation is correct.
Let’s encrypt !
In order to simplify the calculation, we are going to take following values for n, p, q, e and d. We take 5 for the value of e because gcd(5,phi(n)) = gcd(5,12) = 1. This will simplify the process.
To sum up : n = 21 p = 7 q = 3 e= 5 d = 19
The couple (d,n) represents the private key (decrypting key)
The couple (e,n) represent the public key (encrypting key)
Now we are going to compute a message say a number m = 12 (we take this value because this value must be smaller than n) and c our encrypted message that is going to be sent to Bob.
We just need to write
The result of this formula is : c = 12 5mod 21 and then we see c = 3
Decrypting is easy, you just need d ( the private key) and apply following formula :
So 35 mod 21 = 12 <=> m = 12 Bingo 😉
What you just need to know about RSA :
Encrypting
with the couple (e,n) the public key
Decrypting
with the couple (d,n) the private key
Timbaland and Nelly Furtado vs. a C24 Sound
Feb 19th 2007
This story might been dugg x-times but I thought it was pretty interesting 😉 Do you know Nelly Furtado’s hit song ‘Do It’ and the jazzy-electro sample ?
More >
2006 Music reviews
Dec 31st 2006
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Rudebox meets the Lego Box !
Sep 1st 2006
The small animation you have seen on the front page is called “Rudebox meets the Legobox” and I´ve posted it to www.rudebox74.com in order to participate to the Rudebox Competition. I´ve also designed the stickers for the Adidas Sweat shirts worn by the Legos. The background and the street were also designed and printed on paper.
Two little halogen lamps were placed over the scene in order to give an “underground” light condition. In order to have a coherent scenario, I´ve followed Robbie´s original “Rudebox” video. Hope you like my clip 😉
More >
Paper cars
Dec 16th 2005
I’ve found a very interesting new way to build cars! It’s very very cheap : paper cars. Here are some of my favourite sites where you can download PDFs to print, to cut and to stick it up with glue: 3DPapers.com.tw or Streetpaper.de
Depending on the difficulty level, you can realize some very beautiful cars. I’ve decided to build the 360 Modena and the Ferrari F1 2000. By clicking on the pictures you can enlarge. The Modena took me (i’m a beginner, so excuse the imperfections 😉 ) 4 hours and the F1 about 5h30 to build… It’s worse to try!
Le Platt
Apr 25th 2005
Afin de faire profiter au plus grand nombre de visiteurs de mes recherches Internet sur cette langue, vous trouverez ici les articles de Hélène Nicklaus (auteur de “Le Platt” aux Editions Pierrons-Sarreguemines) publiés dans le Républicain-Lorrain ainsi que divers liens sur cette langue. Hélène Nicklaus est également directrice des Ateliers du Platt
Le platt est une langue parlée dans le Nord-Est de la Lorraine et le nord et l’ouest de L’Alsace. Le francique est considéré comme une des langues régionales de France. Le platt est le terme le plus utilisé par les Lorrains pour désigner le francique lorrain. (Définition Wikipédia) More >
My Lego constructions
Apr 25th 2004
I like to play with Lego 😉 This page shows my collection of Lego constructions. | |||||||||||||||
Ferrari (2004) |
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Pieces : 750 Time taken to build the model : Approx 2 hours | |||||||||||||||
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