2007

Software — View Comments
31
jul 07

IE7 certificate check

Internet Explorer 6 had a local list of trusted certificate authorities, when accessing a secure website, it would check locally if the certificate is valid and return right away to the user. When Internet Explorer 7 was released, it came with a new idea, the list came empty and IE7 had to communicate with Microsoft datacenter to check it’s status.

If it is valid, then it will show a green background in the URL prompt, if it’s not or it could not communicate with the datacenter, it will show a red background in the URL prompt and a warning page will appear explaining that it is not recommended or secure to proceed.

Hotspots operators work in a very common way, they block all the traffic until you authenticate, everytime you try to access a website, you’ll be redirected to a captive portal, there you can type your username and password and finally have full access to the internet.

If it’s a good hotspot operator, the captive portal will be secure, but before showing the page, IE7 needs to check if the certificate is valid and you are not authenticated yet. All the packets are dropped, no answer comes and you’ll see the red page warning you.

Walled garden is a common solution for similar problems, where you need to communicate with a host before authenticating. In this case, you need to communicate with Microsoft to check if your certificate is valid. Sniff IE7 communicating with the datacenter, find the host and port and unblock it.

By that time we’ve identified that it was the same host used by Windows Update client. Imagine the structure needed to handle all the users of the world trying to update their windows or checking if a certificate is valid.

We ran a script for days to register the number of hundreds of servers and there was more, Microsoft had a load balacing solution based on the DNS, every fifteen seconds or less the ip of the host changes, this way they are able to balance requisitions.

Obviously we had to use another solution to make the communication with Microsoft possible before authentication. Our certificate was valid, there was no reason for the user to see that red page. It’s a browser that owns more then half of the market and it was a very complicated problem to fix by that time. I had long talks with Microsoft engineers about this issue until they could find a solution. That’s how a software release from a major company and a very silly problem could break a global and mature business segment.

Software — View Comments
11
jul 07

Emacs Flymake

http://blog.marcelotoledo.org/wp-content/uploads/2007/07/emacs-flymake.flv

I have a lot of friends that use Vi, one of them today was around and catched me working on a C program inside Emacs. He got impressed by one of the Emacs modes called Flymake, it does on-the-fly spell checking and I was using it with the gcc compiler. I’ve recorded a video to show how this mode works.

Business — View Comments
26
jun 07

Writers created WiMAX

I want a base station that will cover a very large area, including indoors and will serve hundreds of users at the same time with wireless broadband internet. This is the dream solution, now let me tell you what WiMAX is.

The myth is that WiMAX will deliver 70 Mbit/s, over 48 km (30 miles). Each of them is true individually, given ideal circumstances. Either you have high bandwidth or long reach, not both simultaneously.

The limitation is that like any other wireless system, available bandwidth is shared between users in a given radio sector. If you have a base station capable of covering 2 km (1.2 miles) at 10 Mbit/s and has to serve ten users at the same time, you’ll be delivering 1 Mbit/s for each. Extra radio cards might be added to the base station, but the technology is limited and a lot more expensive for the given results.

One of the good things about WiMAX is that it will – also – be used in the licensed spectrum, creating a better organization of frequencies, which in theory will make sure interference isn’t a problem and considering this the allowed power might be increased in the future. The only concern is the timing of political decisions that take years to accomplish.

This year we already had two of the most important events about wireless in the world, they are CTIA Wireless in Orlando and The Wireless Event in London. Want to know what they said about WiMAX? The same thing they told us two years ago. WiMAX is taking over the world.

Companies don’t install networks because users wouldn’t be able to use, simply because there are no devices (notebooks, cell phones, palmtops, …) available in the market. On the other hand, companies don’t produce devices because there are no networks available.

One good example is Sprint that thought it was the dream solution, they announced in mid-2006 a 3 billion dollars project to cover United States with WiMAX. Investors balked at the cost and they are now thinking about selling the business, or partner with another company, not to mention the worst scenario.

Engineers has created a good system called WiMAX, it is ready for production but the market still need time to mature and establish a good business model. There is one other fantastic technology called WiMAX, this one has been developed by journalists and writers, it’s a dream solution, one base station for miles and miles of indoor coverage, hundreds of users at the same time with broadband internet access, and better, it will happen sooner then you think.

Business — View Comments
23
jun 07

Do you buy spam?

Once again today I heard people complaining about Spam, to be honest, I thought they were talking about canned meat, but no, spam still a big issue in these people’s life.

We experienced that blacklists, authentication and old fashioned forms will never block spam. Spammers already learned that, if we do this, they have to find another way of sending it, so they simply hack into your account and send it from there.

Spam exists because makes total sense to use it as a marketing tool, it’s cheap, viable, easy to find a company to send it for you, and what’s more important, you’ll see results.

It’s a tough economical problem, we don’t see that much physical spam, because it’s expensive, also happens with telephone spam, it’s expensive and people hate receiving those calls, which makes it
inefficient. Excluding the people that is reading this, all the rest buy spam.

The only solution for zero traffic of spam, is it becoming economically inviable. This will only happen when it stop giving results or it become expensive.

The amount of spam I’ve been receiving has increased substantially, but I use a mail client with a spam catcher and it works 99.9% of the time, this means I haven’t seen almost none of them. For me it’s an answered problem. If people don’t receive spam, they can’t read it and then it will break the business model. Part of the solution is in your hands, don’t complain, do something.