Data commit

Task/Vigen-re-cipher/Lua/vigen-re-cipher.lua

@@ -0,0 +1,42 @@
+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 )