Vigenère cipher: Difference between revisions

<pre>WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY

BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH</pre>

=={{header|Lua}}==

<lang lua>function Encrypt( _msg, _key )

local msg = { _msg:upper():byte( 1, -1 ) }

local key = { _key:upper():byte( 1, -1 ) }

local enc = {}

local j, k = 1, 1

for i = 1, #msg do

if msg[i] >= string.byte('A') and msg[i] <= string.byte('Z') then

enc[k] = ( msg[i] + key[j] - 2*string.byte('A') ) % 26 + string.byte('A')

k = k + 1

if j == #key then j = 1 else j = j + 1 end

end

end

return string.char( unpack(enc) )

end

function Decrypt( _msg, _key )

local msg = { _msg:byte( 1, -1 ) }

local key = { _key:upper():byte( 1, -1 ) }

local dec = {}

local j = 1

for i = 1, #msg do

dec[i] = ( msg[i] - key[j] + 26 ) % 26 + string.byte('A')

if j == #key then j = 1 else j = j + 1 end

end

return string.char( unpack(dec) )

end

original = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!"

key = "VIGENERECIPHER";

encrypted = Encrypt( original, key )

decrypted = Decrypt( encrypted, key )

print( encrypted )

print( decrypted )</lang>