Secure Virtual Network Computing

With the ever increasing speed of internet data transfer, virtual network computing (VNC) has become a viable alternative to stand alone work stations with duplicate software installations. VNC enables users to access the desktop of a work station remotely via the internet through a slim client computer for the processing of data with heavy-weight applications. Commonly, a window server application needs to be installed on the work station and a viewer application needs to be installed on the client computer to display the work station's desktop. Once the client is connected to the server, the user can work on the server like on any other desktop. Modern VNC versions even allow drag-and-drop file transfer between client and server.

Commercial VNC software is available for Linux/Unix, Microsoft Windows, and Apple's OS X operating systems (e.g. RealVNC). Apple provides simple remote desktop connectivity for its computers in Leopard (ARD 3.2). Redstone Software offers only the Vine 3.0 server for OS X (formerly OSXvnc) free and charges for a sophisticated server/client combination with which you can drag and drop files. However, Chicken of the VNC can be used for viewing on OS X as a free complement to the Vine server.

A great advantage of VNC is that the connectivity between client and server is platform-independent. Their operating systems need not be identical. I currently use TightVNC. TightVNC is an award-winning open source project offering a highly functional package for UNIX- and Microsoft Windows-based operating systems. I installed the server on a computer running Microsoft Windows XP-64. I view the desktop on a machine running Ubuntu 8.10 or on Apple computers running OS X. TightVNC comes with a platform-independent, Java-based viewer that can be used as stand-alone application, provided the Java Runtime Environment (JRE) is installed. JRE is included with OS X and can be easily installed with the Synaptic Package Manager on Ubuntu. In addition, a viewer applet can be accessed on the server through the browser. The latter option does not require any install on the client.

VNC connections commonly use ports with numbers equal to or greater than 5900. The last digits identify the display number. The user needs to register a user account with username and password on the server. The regular login dialog is unencrypted, rendering the server vulnerable to break-ins. This hazard is perhaps tolerable on a local network protected by a firewall. However, if the server is slated to be accessible over the internet at large, unencrypted login exposes the server to excessive risk. Remote login to the server through a secure shell with RSA encryption is preferable and SSH protocols provide this option.

SSH encryption is fairly safe, particularly when passphrase encryption is employed. As additional precaution, the administrator may wish to ascertain that root login is disabled in the SSH configuration script. I once made the mistake to administer a computer with superuser privileges choosing a common English noun as password. I did not know that root was enabled by default as username on port 22 in the SSH configuration script. It took some miscreant five years to guess the password, turning my machine into a reflector for evil data transfer, until the gate keepers found out about it. To preempt complications of this nature in the future, I use sudo these days, if I need to execute commands with superuser privileges.

Remote login to a VNC server from a VNC viewer with SSH entails two steps: first the connection to the VNC server needs to be successfully established via the SSH protocol, and then the viewer has to be opened using the connection. I developed a Java-based application on the intel architecture from open sources for Apple's OS X 10.4 (Tiger) and 10.5 (Leopard) that achieves this goal in a convenient amalgamated process. This sVNC client combines jcraft's SSH login with the TightVNC viewer.

If you like to use the sVNC client, you may wish to download the zipped folder containing the application bundle with a click on the logo on the left (trademark application #77642277, pending). Copy the application to a folder of your preference. Double-click on the application's icon to launch the SSH dialog. You are asked to enter your username @ the VNC server identified by name or IP address. Subsequently, you need to provide a listening port:host:remote port combination, specifying the local host and the ports for the displays. Commonly, you can use the default combination 5900:127.0.0.1:5900. This combination specifies the host and serves from and to displays with the number 0.  If the VNC server uses a different display number, e.g. display 1, change the first number to 5901. If you wish to use a different display on your home computer, you need to change the last number accordingly. There is no need to change the address for the local host.

After you provided this information, the SSH dialog generates RSA keys. Your consent is needed. You must enter your password for the VNC server. The connection is attempted. In case of success, you need to provide your password once more for the VNC viewer, the display of the remote desktop should pop up, and you are ready to go. The configuration options to the viewer can be found in the README file included with the application in the zipped folder.

The client works well for me. If the remote desktop seems unresponsive to clicks, hit the refresh button on the viewer's top panel. The viewer may crash when the server is accessed in a sleep state. Do not be discouraged. The viewer will work on the second attempt. I hope sVNC will be useful to you.

2.5-inch Hard Drive Enclosures: A Journey

Hard drives have become small theses days. I needed a handy external storage device for travels with the laptop. After considering enclosure size and prize range, I opted for a Hitachi TravelStar 200GB 2.5-inch hard drive and sought the enclosure, separately. The latter turned into an adventure.

I looked up enclosures with USB-2.0 connectivity. USB cable and a protective pouch are usually included. The first I ordered from an internet retailer of national renown had a nice steel case and the option to power it with a separate supply that was not included. It cost $30.- and came with a hefty rebate offer. I never received the rebate, because the rebate center did not accept the only proves of purchase I had, that is copies of the order confirmation and the packing slip. You will not see advertisements of this retailer on my sites.

Installation of the hard drive into this enclosure was simple. You had to remove a tiny lock-down screw on each long side, pull out the front of the enclosure with the USB interface, attach the drive to the connector, slip the assembly into the case, and re-secure the front with the screws. Sadly, the drive would not start up.

The next enclosure I bought cost only $10.-. No rebates were involved. Installation was simple. Again, the front needed to be pulled out of from the case, and the drive had to be connected. This time no screws were needed. The drive was supposed to be powered by the USB connection. To my frustration, the drive attempted to start up with plenty of clicks, but did not succeed. What was the problem?

I did not read the specifications in the extended description of the enclosure. Apparently, the USB interfaces of some SATA drive enclosures are limited in the storage size of the drive they can handle. This limitation is not related to the price. I eventually found a suitable enclosure that red.populus offered on ebay for $11.-, shipping and handling included.

The top and bottom shells of Dragonext's USB-2-0 2.5-inch SATA external hard drive case must be slid backward to open the enclosure. The drive must be connected to the interface and secured with four screws to a bottom plate, and top and bottom shells are slid forward over the drive until they snap into the front. Once connected to the computer with the included cable, the drive started up without complaint.

The cable is special in that it sports two USB connectors on the computer-side; one for power and one for data. Taking up two USB connections may seem a nuisance, but constitutes a small inconvenience for a functional case that does not need a separate power supply.

Of course, if you choose to avoid any hassle and are looking for a drive that is more sturdy and extravagant, but bulkier, you may opt for the product below:

Ginkgo & Stroke

Today, Oct. 10, 2008, Tara Parker-Pope informs us in a post under her New York Times health column Well on recent research suggesting that Ginkgo tree extracts may reduce brain damage after stroke. The study is published in the journal Stroke. The researchers affiliated with Johns-Hopkins University and La Fondation Ipsen temporarily blocked the middle cerebral artery in mice to induce an ischemic stroke. In mice treated with Ginkgo extract, the volume of brain tissue affected by the stroke was only about half that observed in untreated mice. The extract had no effect in mice that lacked heme oxygenase 1, an enzyme known to reduce oxidative stress caused by free radicals. These findings may encourage further basic research, ultimately opening a path for future pre-clinical and clinical trials.

I developed a liking for Ginkgo trees ever since I saw my first one on a high school visit to Heidelberg. The tree stood in the park outside the castle, solemnly holding its own one of a kind. They are not native to Germany. A lord long gone had purchased a seedling from China and planted it as a curiosity.

Ginkgo biloba is a species of ancient plants. Herbivorous dinosaurs already dieted on their broad leaves. The leaves are misleading. The trees are more closely related to conifers than to broad-leafed trees. Ginkgos are abundant in the Southeastern United States where I live. The leaves add a wonderful bright yellow to the panoply of foliage colors in the fall.

The leaves' peculiar shape caught the eye of the eminent German poet scientist J.W. von Goethe two centuries ago. Eternalized in a remarkable poem, Goethe calls to our attention the fact that the observer cannot tell from the leaves' shape whether they constitute one leaf split into two or two leaves fused into one. I quote "...Eins und doppelt bin."

This notion of ambiguity applies immediately to the discussed stroke research. As long as we do not know precisely which substances in the Ginkgo extract affect the ischemic brain tissue and what underlying molecular mechanisms reduce the impact of the stroke, medication with Ginkgo extracts is ill-advised. Particular prudence should be exercised, because the extracts are known to diminish blood clotting, exposing patients on blood thinners to additional risk.