This keep happening to me… sometimes, you just can’t beat murphy

Sometimes I wonder why I carry that much stuff in trade shows …

I created my account on their website, and successfully validated my email, but could not ever access the domain validation interface. For those who struggle on that too, here is the key point you need to know :

StartSSL control panel does not work on Safari !!!!! (and since Safari is my main MacOS X browser … I got screwed …)

Now the problem is that when you login (as me) under safari, it creates a .crt file (or .pem depending on how you download it) to validate your access, and that file can not be imported from firefox (Firefox will ask you a password and complain that this file is not a valid PKCS#12 format … how nice ).

Since you created your account and imported this certificate into your prefered MacOS X Keychain program, the trick is to export the key from the Keychain application in p12 format (PKCS#12). In the process you will be asked to set a password for this certificate export. Now that you have your .p12 file, you can import it into Firefox, and you can login again onto your StartSSL interface. The domain validation interface will then appear “magically”

“Comparaison des différentes techniques de transmission de données, Solutions applicables à l’habitation particulière”.

Well, after some 6weeks of sleepless nite, and coffee doping, here it is, I hope this could help someone out there

ELE114-20091216-F. Delizy

Here is the bug description :

1. Connect to orange.fr mobile customer website with a valid user, say ‘A’
2. Go to my vochers and view one of them
3. you’ll be asked to enter a second password, enter the vocher password of ‘A’
4. now, disconnect from ‘A’
5. connect with a valid user ‘B’
6. go to my vochers again
7. and, hell! you’ll see ‘A’’s vochers, no need to enter any password

This means that on any public PC, you will see the vochers of the guy connecting right before you …

Happy hacking

BTW: you’ll be able also to dump his account settings, and hack his phone line from this point, but I’ll let you find how.

We will attempt to define the ideal matrix of the transversal equalizer in a few steps.

Recurrence Equation

Recall on IIR Filter :

If a channel is given a transfer function as

It’s recurrence equation is then (given the output of an inputted signal) :

Thus according to this formula, in this case, the reccurence equation is written:

Polynomial Decomposition of the Z Transfer Function

Recall:

Let to help calculation, then :

This can be also written:

Signal Auto-correlation

Recall:

The Autocorrelation of a random signal going through a filter is defined by the function :

Let’s calculate :

Recall: and in particular, if , then :

Thus, using that equation :

The same reasonning could be done, to find $r_1$ but a smarter way is to notice that :

In general, you could proove that

Hence the auto correlation matrix is

The rest is just basic formula application to find the matrix, first determine , then multiply by the matrix (with ) and you got it.

Sorry guys, this blog is full English, so this page will be in English as well, but maths are international, you’ll get it for sure

Well, I’ll be giving some hints on the correction of the 2003/09/06 exam, let’s see how far I can go on that :

Q: A digital filter has the following transfer function :

Give the relation between the input and the output . Give the expression of it’s impluse response.

To understand this problem, let’s remind some basic points about Infinite Impulse Response filters. An IIR (French: RII) has an infinite number of coefficient to its impulse response, basically, depends on the first ever sent. To this extend, we can say that whatever the IIR Filter having its transfer function, can be written :

In our case, is a rationnal fraction, so we can use the polynomial division to calculate the first coefficients, and hopefully express all coefficients, let’s go :

We could continue this division forever (remember this is an infinite impulse response filter), but coefficients are gonna cycle, and we could find an expression giving them all.

Hence the relation between the input can be written :

The Impulse Response can be calculated as

]]> http://www.unfreeze.net/?feed=rss2&p=129 0 http://www.unfreeze.net/?p=109 http://www.unfreeze.net/?p=109#comments Sun, 13 Sep 2009 09:20:35 +0000 goutnet http://www.unfreeze.net/?p=109 Recently on a familly meeting, I’ve been asked to send my math book list to a cousin (hope him to go threw them for his own good).

Well, this is reminding me that I planned (long time ago) to open a book section containing the books I had the chance to get my hands on that will be done in a near future, stay tuned

well, I thought there were some interest in being a French expat (or working abroad), so I googled a little bit, and here is what I found:

http://droit-finances.commentcamarche.net/contents/impot-revenu/imp10-impot-sur-le-revenu-notion-de-residence-fiscale.php3

Some people told me you don’t need to pay taxes if you work abroad for a certain amount of time, well it’s wrong:

• As mentionned in the above article, your activity must be in construction field, ressource mining, or sales.
• If you are in construction you’ll end up after 183 days of work to have some exonerations of tax
• If you are in sales, and your activity is about installing a new company abroad, you’ll need 120 days
• In any case, you can only “not pay” taxes relative to your salary when you are abroad (120 days/183 days), but that does not concern the rest of the year.

Isn’t it great ? I mean wouldn’t it be great, if I were ever working in those fields…

References (for those who are interested, beware French law text, in French):
CGI.81.A

This tutorial assumes you are trying to install a DNS server on your local network, under debian amd64, and that you want to use external DNS servers for forwarding external requests (ie: you are not an Internet DNS server)

In the next sections, your.domain.com must be replaced by your actual domain name, and 192.168.0.1 its IP address. Moreover, the configured zone is 192.168.0.0/24 and must be changed accordingly.

Basic installation and configuration

First of all you got to install the bind9 package:

apt-get install bind9

Edit the main configuration file /etc/bind/named.conf.options and add or uncomment the forwarders line, and add your external DNS:

forwarders {
       212.27.53.252;
       212.27.54.252;
};

Those lines implies that all requests your DNS does not know will be forwarded directly to the forwarders.

In the options block, add the IP the server must listen to:

       listen-on {
                192.168.0.1;
                127.0.0.1;
        };

to allow incoming requests only on those addresses (replace by the actual IP address of the server). You can add as many addresses you need.

Start, or restart the DNS server:

invokerc.d bind9 restart

Then edit the server’s /etc/resolv.conf:

search your.domain.com
nameserver 127.0.0.1

On your client machine, you will have to replace the line nameserver 127.0.0.1

To test if your server is corerctly working, you can use the command nslookup:

 you@yourhost:/some/place$ nslookup www.yahoo.fr
Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
www.yahoo.fr    canonical name = www.euro.yahoo.akadns.net.
Name:   www.euro.yahoo.akadns.net
Address: 217.12.3.11

For now, your server is acting as a DNS cache…

Add DNS zones

Once your DNS server is configured (see preceding section), you can add zones to it. Firs tyou have to edit the main configuration file /etc/bind9/named.conf and add the next block:

zone "your.domain.com" {
        type master;
        file "/etc/bind/db.your.domain.oom";
};

zone "0.168.192.in-addr.arpa" {
        type master;
        file "/etc/bind/db.192.168.0";
};

The first zone is the network your.domain.com, and the second define reverse lookup zone 192.168.0.* (change accordingly). Notice the inversion of the IP address notation, in DNS lookup zones, addresses are spelled backward.

Now create the file /etc/bind/db.your.domain.com and add:

$TTL    604800
@       IN      SOA     ns.your.domain.com. your_email@your.domain.com. (
                              1         ; Serial can be replaced by a number like YYYYMMDDNN where NN is an incrementing number
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@                IN      NS      ns.
@                IN      A       192.168.0.1
ns               IN      A       192.168.0.1
host1            IN      A       192.168.0.2

Add as many host you need (syntax: hostname IN A address). Pay attention to the ‘.’ at the end of your domain name and email.
The Serial field is an incrementing number, admins usually take the convention to put the date in it (like mentioned in the comment), to track modification dates, but this is not mandatory.

Finally create the /etc/bind/db.192.168.0 file:

$TTL    604800
@       IN      SOA     ns.your.domain.com  your_email@your.domainfdy.f4-toys.com. (
                              1         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@                       IN      NS      ns

2                       IN      PTR     host1

This file is the reverse DNS lookup database, add as many hosts you need.

Restart again the DNS server

/etc/init.d/bind9 restart

You can also restart your server by invoking rndc:

rndc restart

Automate the client DNS configuration with dhcpd

To auto configure your clients on the DHCP network, add the following line to your dhcpd.conf file:

option domain-name-servers 192.168.0.1;

That’s all, happy DNSing