Security Card API

--Security Card API

 local password = "Password for Encryption"
 --You could change this per computer or have it the same...
--up to you really I would save it somewhere on the computer encrypted
--so a password is needed when the computer boots up to let anyone with
--the card through but that might be awkward in multiplayer


function encrypt(msg,pass)
    -- msg= (32-126)
    local str =""
    local key = 0
    msg= msg:reverse()
    for  x = 1, #pass do
        key = key + pass:byte(x)
    end
    key = (key+2)%50
    for x = 1, #msg do
        local ch = string.byte(msg,x)
        ch = ch - key
        if(ch<32)then
            ch = 126 - (32-ch)
        end
        ch = string.char(ch)
        str = str..ch
    end
    return str
end

function decrypt(msg,pass)
    -- msg= (32-126)
    local str =""
    local key = 0
    for  x = 1, #pass do
        key = key + pass:byte(x)
    end
    key = (key+2)%50
    for x = 1, #msg do
        local ch = 0
        local t = 0
        ch = string.byte(msg,x)+key
        if(ch>126)then
            ch = 32 + (ch-126)
        end
        ch = string.char(ch)
        str = str..ch
    end
    str= str:reverse()
    return str
end

function setDiskLevel(side, lvl1, lvl2, psw)
    if fs.exists("disk/level") then
        fs.delete("disk/level")
    end

    local h = fs.open("disk/level", "w")
    h.writeLine("level1:"..encrypt(lvl1,password))
    h.writeLine("level2:"..encrypt(lvl2,password))
    h.writeLine("Password:"..encrypt(psw,password))
    h.close()
    disk.setLabel(side, "Level: "..lvl1.."-"..lvl2.." Card")
end

function getDiskLevel(side)
if fs.exists("disk/level") then
    local h = fs.open("disk/level", "r")
    local lvl1 = decrypt(string.sub(h.readLine(), 8),password)
    local lvl2 = decrypt(string.sub(h.readLine(), 8),password)
    local psw = decrypt(string.sub(h.readLine(), 10),password)
    h.close()
    return lvl1, lvl2, psw
else
    return false
end
end