In life you love someone and marry some one else
The person you marry becomes your wife or husband &
The one you loved becomes the password of your e-mail id!
Though, this is a forwarded joke making rounds on the net, it has significance with respect to the security of free e-mail services used by millions of people across the globe.
The only security measure available in free e-mail services like Yahoo!, Rediff or Gmail for text messages is the login password. In addition they use Secure Socket Layer (SSL) protocol for financial transactions on net. But none of these e-mail services provide security for text messages ranging from official communications to forwarded messages.
As we all know, the majority of e-mail users tend to keep the following as their passwords:
Spouse’s name
Children’s name
Birth date
Anniversary date
Favorite sports star/film star/author, ex-lover, pet name etc.
In such a situation an intruder who knows your personal details could easily hack into your inbox using the simple trial and error guess game (Brute force attack).
Alternatives available:
Choose a cryptic password which might be difficult even for the composer to remember
Go for digital signatures.
All of us who have studied Cryptography would have definitely come across monoalphabetic ciphers and polyalbahbetic ciphers. While monoalphabetic ciphers are easier to break through (Cryptanalysis is easier) it is not so easy with polyalphabetic ciphers.

An encryption tool
Mr.C.K Mari Gowda and Mr.Mahesh.G who currently work at Acharya Institute of technology, Bangalore, as senior faculty members have come out with a simple security tool (which makes use of a time-tested cryptographic polyalpahbetic substitution algorithm) for e-mail applications.
Using this, we can encrypt the text messages sent from our e-mail application and it can be deciphered only by the receiver who possesses a “secret key” to the message. The intruder who successfully breaks the receiver’s password can only view a cryptic cipher message (an unintelligible message) and not the actual content. Thus a two level security is provided in e-mails.

Operation:
The goal (as mentioned) is to provide a two level security to free e-mail services like Yahoo!, or Gmail. All that is needed is to incorporate two more buttons on the user interface of mail applications namely “Encrypt” and “Decrypt”. Once the message is composed the sender has to click the “Encrypt” just prior to clicking “Send”.
At the receiving end, only a legitimate receiver can decipher the encrypted message by following a series of instructions.

Strengths:
The uniqueness of this application is that any one wanting to decipher the cryptic message will have to try out 128 x 128 combinations of all available alphabets, numerals and special characters on the keyboard.
Limitations and future enhancements:
The current version of the tool works only for text messages, and these two enthusiastic faculty members are working towards incorporating the tool for attachments comprising of graphics and animation also.

An improvised idea
The same idea has been implemented at www.mobrien.com for text messages but the improvisation done by these two engineers is by incorporating a second level security for audio/video and compressed attachments.
The cipher needs a plaintext/ciphertext and a key to start. These are tidied by removing all non-alphabetic characters, and capitalizing what remains. The tidied key must not be zero length. Firstly, each character in the text is assigned to a character in the key, like the given matrix. In the given matrix of alphabets, cipher text is formed by comparing the KEY with the plain text characters.
In our example KEY is LANKA and plain text is WORLD CHAMPIONS.
We compare L in row with W in column, the intersecting point of these two letters is H and it is the cipher text.
WORL becomes HOEV and again ‘O’ replaces ‘D’ and so on until entire plain text WORLD CHAMPIONS is encrypted. A simple and effective tool isn’t it?