Trying to make a key encryption/decryption?

[Lua Hal]

Code: Select all

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","1","2","3","4","5","6","7","8","9","0","_"," "}
function index(tab,key)
	for i = 1,#tab do
		if string.lower(tab) == string.lower(key) then
		return i
		end
	end
end
function encrypt(key,value)
	str,text=key,value
	num=string.len(text)
	string=string.rep(str,math.floor(num/string.len(str))) --string.sub includes syntax
	remainder=num-string.len(string)
	longpass=string..string.sub(str,0,remainder)
	for i = 1,#string.len(text) do
		if index(table,string.sub(text,0,1))+index(table,string.sub(longpass,1,1)) ~= nil then
		text=string.sub(text,0,i-1)..table[(index(table,string.sub(text,0,1))+index(table,string.sub(longpass,1,1)))]..string.sub(text,i+1)
		else
		local temp=table[(index(table,string.sub(text,0,1))+index(table,string.sub(longpass,1,1)))-#table]
		text=string.sub(text,i-1,i-1)..temp..string.sub(text,i+1)
		end
	end
	return text
end



function love.draw()
love.graphics.print(encrypt("a","Hi"),0,0)
end

It should translate a string based on this:

Every key is replaced with the sum of that keys numerical value in the table and the numerical value in the password repeated to be the same length as the translated strings value in the table

Let;
H=1
L=2
M=3
N=4

password is "HL"
to change = "HLLH"

1. Password is lengthened to 4 characters long (repetition) ("HLHL")
2. String is translated by adding password and string

HLLH + HLHL

HLLH (1221)
HLHL (1212) +
HNMM (1433)

Sums do not cross over, but instead re-wrap around the table when they exceed #table As in:

#table is 3
Sum is 4
Sum becomes 1
(1,2,3) *loop around* (1)

Thanks in advance

[Taehl]

Aah, the good old Vigenere cypher. Here's a function which does pretty much the same thing you do, except in a more optimal way. Please note that this version won't really produce human-readable results, since it uses all 256 ASCII characters (the full byte). Also, just so you know, the way you have it set up, you're re-encrypting the text every frame (you probably should encrypt once and save the result to a variable).

Code: Select all

function encrypt(key, plaintext)
	local cyphertext = ""
	for i = 1,string.len(plaintext) do
		local ki = i % string.len(key)
		if ki==0 then ki = string.len(key) end
		cyphertext = cyphertext .. string.char( (string.byte(plaintext, i,i)+string.byte(key, ki,ki)) % 256 )
	end
	return cyphertext
end

function love.load()
	result = encrypt("a","Hi")
end

function love.draw()
	love.graphics.print(result, 0,0)
end

Decryption in a Vigenere cypher, by the way, works in exactly the same way, except you subtract they key instead of adding it. Hope this helps.

[Lua Hal]

Thanks!

[Codex]

What would something like this be good for in a game?

[mickeyjm]

What would something like this be good for in a game?

Confusion