In 1966, Seymour Papert and Wally Feurzig developed the Logo Programming Language. As a part of this, Turtle Graphics was a very simple way of teaching programming to children. It consisted of a robotic turtle starting at coordinates 0, 0 in the X-Y plane on a computer screen. With a command turtle.forward(20), the turtle would move forward by 20 pixels in the direction it was facing, drawing a line as it moved. To turn the turtle where it is standing, a command turtle.right(30) would make it rotate 30-degrees clockwise. By combining the two commands and a few others, drawing intricate pictures and shapes on the screen was possible.

Now, the Python standard distribution contains a module “turtle” that allows extending the re-implementation of Turtle Graphics. You can run this on your tiny credit card sized inexpensive single board computer, the Raspberry Pi or RBPi. The Python module tries to keep the same merits as available with Turtle Graphics and is nearly fully compatible with it. That means the learning programmer can use the same commands, classes and methods interactively, when using the module.

For example, if you want to find out where your turtle is at present, you can query it with turtle.postion(), and the turtle will respond with its current X & Y coordinates. Now you can command it to move forward or backward, turn right or left and even check its orientation. For a complete list of the turtle commands, look up module-turtle. Apart from moving in straight lines, you can command the turtle to move in a circle of a given radius.

The Python module turtle is a versatile program. Various commands make the turtle do different things. For example, you may want the turtle to move but without drawing any line. Another command can make the turtle leave a stamped mark at its current position. Yet another command can make the turtle invisible, and another can make it draw lines in the color you specify.

Since RBPi is for children who are starting to learn computer programming, the combination of Turtle Graphics and RBPi is a powerful way of teaching them the basics of robotics. The language used by the module turtle is very similar to every-day English, which makes it very easy for children to learn and use.

Children find it difficult to grasp the abstractions on which traditional Euclidean geometry is built. For example, how do you have a point without size or a line that has a length but no thickness? Young people find all this difficult to grasp. However, the turtle being a real concrete object can be seen and manipulated. Turtle geometry being body syntonic, is easily understood since the turtle moves about just as everybody does. That makes it easy to identify with and its actions are well understood by kids.
Seymour Papert has explained the rationale behind turtle geometry in his book Mindstorms.

Another very simple way of learning turtle graphics on the RBPi is through Kids Ruby. Overall, with Turtle Graphics you can teach absolute beginners the concept of storing algorithms and running them so that the computer will simply obey the given commands.

In almost all airports, hotels, libraries, schools and restaurants, there is a proliferation of free unencrypted wireless access points, which are easily accessible to all. Additionally, with the spread of mobile devices, getting on the internet is no longer confined to the office or the home. Usually, a high number of users share the same open access point. Although this arrangement is very convenient for the users, it is also favorable for the snooper with the skills and intent to invade into others’ privacy and collect internet traffic for nefarious purposes.

Security professionals cry themselves hoarse while preaching restraint when it comes to using free/public wireless access points. However, for users wanting to access their office via the Internet, other than waiting to get back home, very few alternatives are available that are practical, free to use or at least almost free. However, the situation can be easily rectified with an inexpensive Single Board Computer, the Raspberry Pi (RBPi) in conjunction with the freely distributed OpenVPN software.

Offices/homes (SOHO) usually have a private network, which remote devices such as tablets and mobiles access through a typical Remote-Access Virtual Private Network (VPN) configuration. The mobile (the client) must authenticate itself successfully and the VPN server then establishes an encrypted tunnel. Now all traffic between the server and the client via the Internet will be securely routed to the private network through this tunnel, simply as if the mobile (client) had connected directly into the network itself. As the traffic is encrypted, anyone listening in will not be able to decipher the content, and the communication remains safe.

Such an arrangement as described above is very easily implemented with OpenVPN, which is an open source VPN implementation that was developed by James Yonan. OpenVPN is a highly customizable solution and supports a huge range of capabilities and options, including the most relevant five:

• Authentication and encryption ensures privacy
• Protection against Denial of Service and zero-day vulnerabilities
• Protection and privacy through proxy
• SOHO network access
• Broad device supports

OpenVPN was created for ensuring privacy, authentication and encryption, which it does via implementation of SSL/TLS concepts. Two encryption modes are used: Pre-Shared Key and TLS. Pre-shared key concept uses static keys that must be generated and shared with all devices for authentication, to establish and encrypt the secure VPN channel. This arrangement is more like a single lock with multiple users, each holding a key. TLS is a more secure arrangement with private/public key pairs.

To defend against Denial of Service or DoS attacks and Zero-day vulnerabilities, OpenVPN implements a variant of the HMAC key protection. Use of proxy disallows sites such as Amazon, Google or Facebook to establish the VPN client location since they are solely based on the IP address. This provides additional protection for the mobile device, since the Internet traffic is routed through the SOHO network. SOHO networks usually deploy additional boundary security, such as IPS, and this protection is extended to the mobile device when it connects through the VPN.

The OpenVPN service provides secure access to the resources available on the SOHO network without opening extra ports through the firewall. The device support is broad and covers Windows, Mac OSX, Linux and Android. For implementation on RBPi, more information is available here.