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Questions tagged [vigenere]

Vigenère cipher is an encryption algorithm developed in 1553 and was considered uncrackable until the middle of the 19th century.

Application:

In order to encrypt text, you need to choose a word, W, and the encryption table.

Now, you encrypt the mth letter in the text you want to encrypt using a letter from the word W that was chosen before according to the following formula: 

Em = L(m % n)

where:
m — the serial number of the letter n the text
Em — the letter for the m letter in the text
n — the length of w
L — the letter in w in the specified index.

Now, in the encryption table you go to (Em,Tm) (Tm is the m letter you encrypt), and write the letter that's written there, instead of the original letter.

The encryption table 

 |a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|
------------------------------------------------------
a|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|
------------------------------------------------------
b|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|
------------------------------------------------------
c|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|
------------------------------------------------------
d|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|
------------------------------------------------------
e|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|
------------------------------------------------------
f|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|
------------------------------------------------------
g|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|
------------------------------------------------------
h|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|
------------------------------------------------------
i|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|
------------------------------------------------------
j|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|
------------------------------------------------------
k|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|
------------------------------------------------------
l|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|
------------------------------------------------------
m|m|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|
------------------------------------------------------
n|n|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|
------------------------------------------------------
o|o|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|
------------------------------------------------------
p|p|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|
------------------------------------------------------
q|q|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|
------------------------------------------------------
r|r|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|
------------------------------------------------------
s|s|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|
------------------------------------------------------
t|t|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|
------------------------------------------------------
u|u|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|
------------------------------------------------------
v|v|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|
------------------------------------------------------
w|w|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|
------------------------------------------------------
x|x|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|
------------------------------------------------------
y|y|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|
------------------------------------------------------
z|z|a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|

More information at Wikipedia under Vigenère cipher.

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