September 6, 2013

Yubikeys for two-factor VPN authentication on windows 7

Filed under: General — Tags: , , , , , , , — Arne Joris @ 9:43 pm

yubikeyWe recently implemented two factor authentication for VPN access to our LAN. We use Yubikeys from Yubico to provide one time passwords (OTPs) which, when combined with the domain login and password, protect us from an array of attacks that password-only solutions can never solve.

You hang yubikeys on your keychain so you always have them with you and there are zero interoperability concerns (unlike smartphone solutions such as google’s authenticator). A yubikey requires no battery but draws its power from the USB port you plug it into. To your computer, it looks just like a keyboard, and pushing its green button will make it type 44 letters followed by <enter>, as if you typed it.

yubikey2We wanted to use the standard windows VPN client built into windows 7, so we can connect from any computer running windows 7 without having to install custom software. In the most straightforward deployment, you append your Yubikey OTP to your normal domain password. But it turns out that the windows 7 VPN client supports a maximum of 48 characters for the password, after which it starts truncating from the start of the password. Since the yubikey OTPs have 44 characters, that supports only passwords up to 4 characters, which of course is far below the acceptable range of domain password strength.

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February 18, 2013

Enum: the ‘simple’ C# value type we love to complicate

Filed under: Development — Tags: , , , , , — Arne Joris @ 12:20 pm

Enums are simple collections of constant values, using an underlying integer to store the value.  Enums implement IComparable, IFormattable and IConvertible while still being value types and give us everything we need to store and use things like status values, action codes, colours etc…

You can use enum values in both server and client code, but when the user interface displays an enum, or when the user must be able to choose enums from a combobox, we can run into complications with enums. Making enum display values more human readable and showing values in a particular order are not that easy to implement. In this article, I will show you a solution used in a WPF client consuming WCF web services.

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January 11, 2013

A .NET-based user interface for MATLAB applications

Filed under: Development — Tags: , , , — Arne Joris @ 6:58 pm

logo_matlab MATLAB is a numerical computing environment for engineering applications. It supports communicating with and controlling hardware and processing and visualizing data from that hardware, which makes it a very popular platform for writing the software that goes with custom hardware solutions.  It also supports creating user interfaces too, but they tend to look outdated and clunky. matlabGUI_example1a

For example, the control and display software for your custom pump controller system can easily be written in MATLAB. It would run on a PC that is connected to your hardware, lets the user turn the system on and off, set parameters such as pump cycle delays and display graphs showing overall efficiency or total energy input. You can compile all the MATLAB code and sell it, along with your hardware and the MATLAB compiler runtime, as a product.

But what are your options when you want a sleeker, more modern UI with a ribbon bar, interactive graphs and UI themes or skins?  The most economic solution with a relatively short time-to-market, is to create a .NET based UI which connects to your MATLAB functions. In this article, I’ll elaborate on how exactly this works.

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December 17, 2012

Are you a pointy haired software manager?

Filed under: Development — Tags: , — Arne Joris @ 4:11 pm

Ah, managers… We all love to hate management, until of course we join its ranks. Then we like to think we are different from those other pointy haired types, but we fail to see the evidence to the contrary.

If you recognise some of your own behaviour in the anti-patterns in this article, it is time to re-evaluate! Admitting you are a pointy haired boss is the first step toward better management.

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November 16, 2012

SCRUM: beyond better software

Filed under: Development,Small Business — Tags: , , — Arne Joris @ 6:24 pm

Agile software development has been picking up steam in the last couple of years and especially SCRUM has become a very popular development methodology. SCRUM can produce better results for complex projects and the internet is full of helpful tips on how to tailor it to specific project types, team structures or industries.

I have been using SCRUM for several years now,  in both large and small environments and found that there are  non-technical benefits from the SCRUM process that can have a positive impact on your business. Benefits such as effective customer engagement, timely customer payments and better estimates should be of interest to everyone in the software development business. Small companies may benefit the most because the link between a developer’s pay cheque and customer happiness is obvious and there can be direct contact between end user and developers.

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October 26, 2012

WPF style resources bug causes stack overflow in .NET 3.5

Filed under: Development — Tags: , , — Arne Joris @ 8:12 am

XAML logo We recently re-wrote an AutoCAD 2010 application to be entirely based on .NET.  Our application was using Windows Presentation Foundation for the presentation layer, which lets you nicely separate presentation from business logic using the MVVM pattern.  Since this application also had to run in AutoCAD 2009, it had to use the .NET 3.5 version.

It turns out there is a bug in .NET 3.5 (fixed in 4.0) that causes a stack overflow exception when you define two or more default style resources for the same type at the same level.  If you use global resource files and window-specific default styles, you may run into this and its not at all obvious what the problem (or the solution) is.

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October 18, 2012

SQLBase

Filed under: Uncategorized — Tags: , — Arne Joris @ 12:10 pm

SQLTalkIconOne of the perks of doing software development for small- and medium sized organisations is that you get involved in all aspects of IT.  In our projects at we have done backup, workstation and router configuration, printer troubleshooting, mail merge support and, of course, database maintenance.
Database administration skills are a must when you develop line-of-business applications, and most of us know our way around the usual suspects: Orace, SQL Server, MySql and sometimes even DB2, Informix or PostgreSQL.

When you specialize in legacy application renewal, you sometimes come across more exotic database varieties. In this article, I’ll share my knowledge of SQLBase , a variety I came across earlier this year.

SQL what now ?

Gupta SQLBase was one of the first relational databases for the PC in the 80s. It has changed owners several times in its 30 years, but currently it seems to target embedded platforms, claiming to be a ‘no maintenance’ RDBMS. But back in the mid to late 90s, SqlBase was still a very popular relational database technology for PC platforms, which is why some of the older legacy apps still use them.

I have been helping a client out with DBA services for an aging 7.6.1 release of SQLBase. To give you an idea of how old that is: the hardware requirements state that you need at least 24MB of RAM available on Windows 95, 98, NT or windows 2000 :-)

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