So, given that passwords shouldn’t or should I say must not be saved in a way that enables anyone (even administrators) to retrieve the plaintext version of a password, we’re talking about some sort of hashing. Whether hashing algorithm it is MD5 (avoid) os SHA1 (and in order to avoid precomputed hashes of passwords (known also as rainbow tables) you should use salting techniques with hashing algorithms), the length of a calculated hash does not depend on the length of the plain text password.

So, why is the length of the password limited to 16 characters? Beats me.

Of course, I recommend developers to use bcrypt instead of SHA or MD5. Bcrypt is very slow (compared to SHA or MD5), which is a good property to have for checking passwords — you don’t want to have a super-fast hashing/crypting algorithm thus effectively preventing brute force attacks.

• Function as a regular thermostat
• Which can be controlled remotely via SMS as well:
  • to check current temperature on location
  • to set desired temperature on location
  • to switch power on or off for the oil boiler (heating furnace) and water pumps
  • to alert via SMS when the temperature drops below a defined threshold

The Netduino/Arduino boards are amazing in that they offer a high level language to control them and create your stuff. You can develop & debug with Visual Studio in case of Netduino boards using the familiar interface and software development skills. There are tons of shields (addons, plugins) available for those boards as well. I’m planning on integrating real time clock, digital temperature sensor and a cellular shield (GSM functionality) and a graphical LCD next. Baby steps.

So, how did I wire the external LED?

First, I had to learn some basics:

1. You have to limit current for the LED, otherwise it will burn
2. You have to drop the voltage, or the LED will burn

You can limit current by using resistors. I used the 5V pin on the Netduino, and LED needs only 2.5V, so I had to halve the voltage and limit current at the same time. You can do this simply by using two resistors. Smart people call this voltage divider. First, I calculated the maximum current that is allowed for the LED, and that is 20mA. Given the 5V voltage and formula V = R*I, the resistor comes out to 5V / 0.02A = 250Ω (Ohm). Given that, I now needed to lower the voltage, which in my case is simple. The formula for voltage divider is Vout = Vin * R1 / (R1 + R2). Now that I know that R1 + R2 should be 250Ω it is easy to calculate that R1 = R2 = 125 Ohm. I actually used 120Ω resistors as I didn’t have 125Ω ones.
So, the LED was lit, but I wanted to control it via software, so I needed a “switching” mechanism. I asked around used NPN transistor for that. I connected the LED output to collector of a transistor, and connected the emitor part of the transistor to ground. Now, we need to tell the transistor to “open up”. I figured I’ll just connect the digital output to base of transistor, but friendly guys on a Slovenian electronics forum suggested that I use a resistor in between. So I did.
The end result? A program, which turns the LED on whenever I press the button. The final schema looks something like this:

This image was made with Fritzing which looks like a very promising project as well.

Vesel sem, da ste se odzvali v tako velikem številu in upam, da bo naslednjič tudi tako.

PersistentDictionary implementation is based on Esent, which is a not well-known embedded database included in all major windows version (XP, Vista, Windows Server, etc).  From the Microsoft Windows SDK blog:

ESENT is used by the Active Directory, Windows Desktop Search, Windows Mail and several other Windows services and a slightly modified version of the code is used by Microsoft Exchange to store all its mailbox data. The ESENT API is available through the SDK and can be used on all versions of Windows from Windows Server 2000 on up

There is a managed wrapper for Esent, part of which is also an implementation of PersistentDictionary. Out-of-the box, the PersistentDictionary implementation only stores simple structures and primitive data types, but it is very easy to modify it to support also classes, which are marked with the [Serializable] attribute. One just needs to change the ColumnConverter class. For your convenience, here is the compiled version of EsentCollections, which enable just that. The usage is fairly simple.

var store = new PersistentDictionary<Guid, MyClass>("test-database");
// save an instance of your class
store[Guid.NewGuid()] = new MyClass { PropertyA = "SomeValue" };

// to retrieve and display all elements, you can
foreach(var key in store.Keys) {
  var retrievedInstance = store[key];
  // now do something with this instance
  Console.WriteLine(retrievedInstance.PropertyA);
}

You have to ensure, though, that your custom class is marked for serialization. You can achieve this like so:

[Serializable]
public class MyClass {
  public string PropertyA { get; set; }
}

You can see that it is very easy to implement simple repositories on top of that — for prototyping needs, where the entities are constantly evolving and changing.

Do note, however, that Esent is not limited to PersistentDictionary. You can query it in different ways, add indexes to it, have many columns, etc. The thing is used by large-scale software like Exchange, nontheless.

I will post a simple example of IRepository implementation shortly. Stay tuned!

Since I’ve had this problem before, and I discussed it with Dejan, I started digging through all of my email correspondence with Dejan, but could not find anything. I checked and changed the collation of a database, still nothing. My best friend, Google, was of no help either. It then struck me. Varchar. It is non-unicode data type. nvarchar is of course, what was needed to fix the problem. It is intriguing though, that all of the other Slovene characters work, but c with caret (č) does not get corrupt as one would expect, but gets converted to c.

A lesson learned, is a lesson earned, I guess. This post is here to remind of this situation next time.

Both YSlow and Page Speed require the excellent Firebug extension, which is an essential tool for web developers. If you don’t know YSlow or Page Speed yet, now is the time to get acquainted.

• ajax views
• route debugging
• menulink helper
• error handling (controllers, views, customization)
• different view results (RSS view result among them)
• model binding
• custom controller factory with a simple Autofac dependency injection demo
• custom view engine (showing how mobile pages can be served by using MDBF) and
• client & server side validation using the interesting xVal framework.

Get all demos in one zip archive

Old design

I guess the old blue theme was looong overdue, so I decided to change it. It took longer than expected, but here we are. I don’t know about “better”, but it is definitely different. And that’s a good thing.

On a related note, I do like the new WordPress 2.7 administration interface.

On Mac OS X, there is Quicklook (just press spacebar on an image), then there is the Preview, but neither is well suited for ordinary photo viewing, where you sometimes crop an image and convert it to another format. IPhoto wants to import images and is most importantly not fast for viewing a single images now and then (or a folder of images). So, I found Xee, which seems great so far.

Now, on my shiny new iMac, it was still booting slow – now this just didn’t feel right. I noticed in the release notes that this issue can be worked around by converting the image back to hardware format 6 (whatever that means). And lo and behold, it boots really fast now. Go to Virtual Machine menu and choose Downgrade Virtual Machine and you’ll be set. Hope that helps!