--[[
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