The Enigma Cipher

There is an interesting encryption technique using some hardware called "three rotor machine" or "The Enigma Cipher". The device was invented by the Germans during the II World War. There will be three rotors, to start with. The plain text will be typed in through the key board. When the first character is typed, it passes through the first rotor and gets encrypted according to the position of the rotor, because the rotor has 26 teeth, one for each alphabet. The first rotor passes it's output to the second rotor and the encryption takes place according to it's position, similarly with the third rotor. The new letter that we get for the plain text character, will be bounced off a reflector and we obtain at the first rotor.

The beauty of this machine lies in the complexity that it imposes by rotating. Initially, the first rotor makes its first move for the first character and the other two rotors remain stationary. Once the first rotor completes 26 moves, the second rotor makes a single move. Even now the third rotor is stationary. Till now, we have 26x26=676 combinations, coz the first rotor makes 26 moves for each of the 26 teeth in the second rotor. When the second rotor completes 26 moves, the third rotor makes a single move. The entire process repeats now. To sum it up, we have 26x26x26=17576 combinations.

The initial position of the rotors act as the key. The decoding people must know the initial configuration to decode the message. In those times, the configuration was written on a diary which had the configuration for each day. This was insecure, coz if someone happens to get the diary, he may form the machine of his own. The Enigma cipher was broken(decrypted secretly) by Alan Turing (In picture) and group of scientists for America. Had this not been broken, the Germans would have had a different course of war!

Proxy Servers

Many a times we have come across the term "proxy servers". Proxy servers are an intermediate link between the "client" and the "internet". When a client sends a request to the internet, its first received by the proxy server and then its forwarded to the internet. The reply from the internet reaches the proxy server and then the proxy server forwards that result to the client. People use different proxy servers depending upon their need. The major types are listed below.

Web Proxy:

This server is used to monitor the contents transferred over the world wide web. These are mainly used in schools, colleges and other institutions where the offensive contents and unauthorized sites need to be blocked for client accessing. In these cases, the client sends a request to the internet, which is received by the proxy server and it forwards the request to the internet. The reply from the internet reaches the proxy server and if any offensive or illegal content is present, the access to those contents is prevented by the proxy server.

Anonymous Proxy:

This proxy server helps to remove information that may identify the person, information that are confidential from the user's request. For example, while accessing the social networking sites like, orkut, facebook etc. the information is at the risk of being known to many people. So, these servers take care of what contents must be seen by which group of people.

Caching Proxy:

This is a special type of proxy in which the proxy server replies to the client's request without contacting the main server. This action is possible when the proxy server has some part of the contents in the main server cached into it's memory and there must have been some information sent to the main server by the proxy that it will be replying to the client directly. This ensures the clients get their queries answered very soon.

Forced Proxy:

Forced proxy just forwards the client's request to the main server in the internet everytime. The client will not know that they are using a proxy site.

Open Proxy:

Open Proxy enables that anybody can obtain a link to this proxy server and use it. This causes security to be breached and facilitates exploitation by spammers. Many organizations deny requests that come from proxies that are known to be "Open".

From the above discussion we see that, proxies can enable faster operation by quickly processing user requests and reduce the load on the main server by serving some of the requests on their own and they also act as firewalls for educational insttutions.