--[[
Diffie–Hellman key exchange in a simple to use library
Note:
this does NOT use big integers
this is designed for computercraft's limited processing power
use a Diffie–Hellman key exchange algorithm that can handle big integers for real-world applications
--]]

local n= 625210769
local g= 11

local secret = 0

local function baseToPowerMod(base,power,modulus)
--This function was taken from Anavrins' Diffie-Hellman proof of concept
--Full code here:http://pastebin.com/H3kZHZBA
local remainder = base
for i = 1, power-1 do
remainder = remainder * remainder
if remainder >= modulus then
remainder = remainder % modulus
end
end
return remainder
end

function createSecret() -- returns public key to send to partner
secret = math.random(1000,9999)
local public = baseToPowerMod(g,secret,n)
return public
end

function handshake(public) -- returns key to use for symmetric encryption
if secret == 0 then error("Secret as not been created",2) end
local key =baseToPowerMod(public,secret,n)
return key
end

function getDoc()
return [[createSecret(): returns public number to send to partner
handshake(int public): returns key to use in symmetric encryption]]
end