-- this function converts a string to base64

function to_base64(data)

    local b = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

    return ((data:gsub('.', function(x) 

        local r,b='',x:byte()

        for i=8,1,-1 do r=r..(b%2^i-b%2^(i-1)>0 and '1' or '0') end

        return r;

    end)..'0000'):gsub('%d%d%d?%d?%d?%d?', function(x)

        if (#x < 6) then return '' end

        local c=0

        for i=1,6 do c=c+(x:sub(i,i)=='1' and 2^(6-i) or 0) end

        return b:sub(c+1,c+1)

    end)..({ '', '==', '=' })[#data%3+1])

end

-- this function converts base64 to string

function from_base64(data)

    local b = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

    data = string.gsub(data, '[^'..b..'=]', '')

    return (data:gsub('.', function(x)

        if (x == '=') then return '' end

        local r,f='',(b:find(x)-1)

        for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end

        return r;

    end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x)

        if (#x ~= 8) then return '' end

        local c=0

        for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(8-i) or 0) end

        return string.char(c)

    end))

end

-- usage

local data = "this is a test"

local encoded = to_base64(data)

print(encoded) -- dGhpcyBpcyBhIHRlc3Q=

local decoded = from_base64(encoded)

print(decoded) -- this is a test

local b='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/' -- You will need this for encoding/decoding

-- encoding

function enc(data)

    return ((data:gsub('.', function(x) 

        local r,b='',x:byte()

        for i=8,1,-1 do r=r..(b%2^i-b%2^(i-1)>0 and '1' or '0') end

        return r;

    end)..'0000'):gsub('%d%d%d?%d?%d?%d?', function(x)

        if (#x < 6) then return '' end

        local c=0

        for i=1,6 do c=c+(x:sub(i,i)=='1' and 2^(6-i) or 0) end

        return b:sub(c+1,c+1)

    end)..({ '', '==', '=' })[#data%3+1])

end

​

-- decoding

function dec(data)

    data = string.gsub(data, '[^'..b..'=]', '')

    return (data:gsub('.', function(x)

        if (x == '=') then return '' end

        local r,f='',(b:find(x)-1)

        for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end

        return r;

    end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x)

        if (#x ~= 8) then return '' end

        local c=0

        for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(8-i) or 0) end

            return string.char(c)

    end))

end

​