aeslua/util.lua

local bit = require("bit");

local public = {};

local private = {};

local aeslua = require("aeslua");

aeslua.util = public;

--

-- calculate the parity of one byte

--

function public.byteParity(byte)

    byte = bit.bxor(byte, bit.rshift(byte, 4));

    byte = bit.bxor(byte, bit.rshift(byte, 2));

    byte = bit.bxor(byte, bit.rshift(byte, 1));

    return bit.band(byte, 1);

end

-- 

-- get byte at position index

--

function public.getByte(number, index)

    if (index == 0) then

        return bit.band(number,0xff);

    else

        return bit.band(bit.rshift(number, index*8),0xff);

    end

end

--

-- put number into int at position index

--

function public.putByte(number, index)

    if (index == 0) then

        return bit.band(number,0xff);

    else

        return bit.lshift(bit.band(number,0xff),index*8);

    end

end

--

-- convert byte array to int array

--

function public.bytesToInts(bytes, start, n)

    local ints = {};

    for i = 0, n - 1 do

        ints[i] = public.putByte(bytes[start + (i*4)    ], 3)

                + public.putByte(bytes[start + (i*4) + 1], 2) 

                + public.putByte(bytes[start + (i*4) + 2], 1)    

                + public.putByte(bytes[start + (i*4) + 3], 0);

    end

    return ints;

end

--

-- convert int array to byte array

--

function public.intsToBytes(ints, output, outputOffset, n)

    n = n or #ints;

    for i = 0, n do

        for j = 0,3 do

            output[outputOffset + i*4 + (3 - j)] = public.getByte(ints[i], j);

        end

    end

    return output;

end

--

-- convert bytes to hexString

--

function private.bytesToHex(bytes)

    local hexBytes = "";

    for i,byte in ipairs(bytes) do 

        hexBytes = hexBytes .. string.format("%02x ", byte);

    end

    return hexBytes;

end

--

-- convert data to hex string

--

function public.toHexString(data)

    local type = type(data);

    if (type == "number") then

        return string.format("%08x",data);

    elseif (type == "table") then

        return private.bytesToHex(data);

    elseif (type == "string") then

        local bytes = {string.byte(data, 1, #data)}; 

        return private.bytesToHex(bytes);

    else

        return data;

    end

end

function public.padByteString(data)

    local dataLength = #data;

    local random1 = math.random(0,255);

    local random2 = math.random(0,255);

    local prefix = string.char(random1,

                               random2,

                               random1,

                               random2,

                               public.getByte(dataLength, 3),

                               public.getByte(dataLength, 2),

                               public.getByte(dataLength, 1),

                               public.getByte(dataLength, 0));

    data = prefix .. data;

    local paddingLength = math.ceil(#data/16)*16 - #data;

    local padding = "";

    for i=1,paddingLength do

        padding = padding .. string.char(math.random(0,255));

    end 

    return data .. padding;

end

function private.properlyDecrypted(data)

    local random = {string.byte(data,1,4)};

    if (random[1] == random[3] and random[2] == random[4]) then

        return true;

    end

    return false;

end

function public.unpadByteString(data)

    if (not private.properlyDecrypted(data)) then

        return nil;

    end

    local dataLength = public.putByte(string.byte(data,5), 3)

                     + public.putByte(string.byte(data,6), 2) 

                     + public.putByte(string.byte(data,7), 1)    

                     + public.putByte(string.byte(data,8), 0);

    return string.sub(data,9,8+dataLength);

end

function public.xorIV(data, iv)

    for i = 1,16 do

        data[i] = bit.bxor(data[i], iv[i]);

    end 

end

return public;