cyph

local aes = loadfile("aes")()
local aesutil = loadfile("util")()
local buffer = loadfile("buffer")()

local public = {};

--
-- Encrypt strings
-- key - byte array with key
-- string - string to encrypt
-- modefunction - function for cipher mode to use
--
function public.encryptString(key, data, modeFunction)
    local iv = iv or {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    local keySched = aes.expandEncryptionKey(key);
    local encryptedData = buffer.new();

    for i = 1, #data/16 do
        local offset = (i-1)*16 + 1;
        local byteData = {string.byte(data,offset,offset +15)};

        modeFunction(keySched, byteData, iv);

        buffer.addString(encryptedData, string.char(unpack(byteData)));
    end

    return buffer.toString(encryptedData);
end

--
-- the following 4 functions can be used as
-- modefunction for encryptString
--

-- Electronic code book mode encrypt function
function public.encryptECB(keySched, byteData, iv)
        aes.encrypt(keySched, byteData, 1, byteData, 1);
end

-- Cipher block chaining mode encrypt function
function public.encryptCBC(keySched, byteData, iv)
    aesutil.xorIV(byteData, iv);

    aes.encrypt(keySched, byteData, 1, byteData, 1);

    for j = 1,16 do
        iv[j] = byteData[j];
    end
end

-- Output feedback mode encrypt function
function public.encryptOFB(keySched, byteData, iv)
    aes.encrypt(keySched, iv, 1, iv, 1);
    aesutil.xorIV(byteData, iv);
end

-- Cipher feedback mode encrypt function
function public.encryptCFB(keySched, byteData, iv)
    aes.encrypt(keySched, iv, 1, iv, 1);
    aesutil.xorIV(byteData, iv);

    for j = 1,16 do
        iv[j] = byteData[j];
    end
end

--
-- Decrypt strings
-- key - byte array with key
-- string - string to decrypt
-- modefunction - function for cipher mode to use
--
function public.decryptString(key, data, modeFunction)
    local iv = iv or {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

    local keySched;
    if (modeFunction == public.decryptOFB or modeFunction == public.decryptCFB) then
        keySched = aes.expandEncryptionKey(key);
        else
                keySched = aes.expandDecryptionKey(key);
    end

    local decryptedData = buffer.new();

    for i = 1, #data/16 do
        local offset = (i-1)*16 + 1;
        local byteData = {string.byte(data,offset,offset +15)};

                iv = modeFunction(keySched, byteData, iv);

        buffer.addString(decryptedData, string.char(unpack(byteData)));
    end

    return buffer.toString(decryptedData);
end

--
-- the following 4 functions can be used as
-- modefunction for decryptString
--

-- Electronic code book mode decrypt function
function public.decryptECB(keySched, byteData, iv)

    aes.decrypt(keySched, byteData, 1, byteData, 1);

    return iv;
end

-- Cipher block chaining mode decrypt function
function public.decryptCBC(keySched, byteData, iv)
        local nextIV = {};
    for j = 1,16 do
        nextIV[j] = byteData[j];
    end

    aes.decrypt(keySched, byteData, 1, byteData, 1);
    aesutil.xorIV(byteData, iv);

        return nextIV;
end

-- Output feedback mode decrypt function
function public.decryptOFB(keySched, byteData, iv)
    aes.encrypt(keySched, iv, 1, iv, 1);
    aesutil.xorIV(byteData, iv);

    return iv;
end

-- Cipher feedback mode decrypt function
function public.decryptCFB(keySched, byteData, iv)
    local nextIV = {};
    for j = 1,16 do
        nextIV[j] = byteData[j];
    end

    aes.encrypt(keySched, iv, 1, iv, 1);

    aesutil.xorIV(byteData, iv);

    return nextIV;
end

return public;