the vigene cipher is probably the easiest cipher which was invented by blaise de vigenere, a french diplomat born in 1523. it's similar to caesars cipher. it works -like the most ciphers- by replacing each letter by another letter.

to encipher, first we create a vigene square(there's no need actually, but that's how original one works, and my implementation based on this one) which is basically a 2d array filled with the letters of the alphabet 26 times, and each letter shifted to the left compared to the previous letter.

here's the vigene square we need to create for encryption.


for example let's encrypt attack at dawn with the key white. to encrypt the first letter a, identify the letter w from the square. the row beginning with w is the 22th row, is the letter that will be used for letter a. then we find the a's equal in the 22th row, which is w. so, a will be represented by the letter w in the cipher text.
for the letter t, procedure is same. identify the row which begins with the letter h, and seek the letter t in that column, which is the letter a. for the third letter, again, t, identify the row which begins with the letter i, and seek the letter t in that column, which turns out to be the letter b. the process is repeated until the end of the message we need to encrypt is reached. so the final encrypted message is;
WABTGGHBWESU

so, if we sum up;


my implementation of vigene cipher removes the numeric values, and encrypts based on the original vigene square. if you want to download it, here's the source files which is written in java, and released under gpl license (gplv3).

the vigene cipher source code in java