Diffie Hellman Key-Exchange in Lua

--    Handshake


local Handshake = {}

Handshake.prime = 625210769
Handshake.channel = 54569
Handshake.base = -1
Handshake.secret = -1
Handshake.sharedSecret = -1
Handshake.packetHeader = "["..protocolName.."-Handshake-Packet-Header]"
Handshake.packetMatch = "%["..protocolName.."%-Handshake%-Packet%-Header%](.+)"


function Handshake.exponentWithModulo(base, exponent, modulo)
        local remainder = base

        for i = 1, exponent-1 do
                remainder = remainder * remainder
                if remainder >= modulo then
                        remainder = remainder % modulo
                end
        end

        return remainder
end


function Handshake.clear()
        Handshake.base = -1
        Handshake.secret = -1
        Handshake.sharedSecret = -1
end


function Handshake.generateInitiatorData()
        Handshake.base = math.random(10,99999)
        Handshake.secret = math.random(10,99999)
        return {
                type = "initiate",
                prime = Handshake.prime,
                base = Handshake.base,
                moddedSecret = Handshake.exponentWithModulo(Handshake.base, Handshake.secret, Handshake.prime)
        }
end


function Handshake.generateResponseData(initiatorData)
        local isPrimeANumber = type(initiatorData.prime) == "number"
        local isPrimeMatching = initiatorData.prime == Handshake.prime
        local isBaseANumber = type(initiatorData.base) == "number"
        local isInitiator = initiatorData.type == "initiate"
        local isModdedSecretANumber = type(initiatorData.moddedSecret) == "number"
        local areAllNumbersNumbers = isPrimeANumber and isBaseANumber and isModdedSecretANumber

        if areAllNumbersNumbers and isPrimeMatching then
                if isInitiator then
                        Handshake.base = initiatorData.base
                        Handshake.secret = math.random(10,99999)
                        Handshake.sharedSecret = Handshake.exponentWithModulo(initiatorData.moddedSecret, Handshake.secret, Handshake.prime)
                        return {
                                type = "response",
                                prime = Handshake.prime,
                                base = Handshake.base,
                                moddedSecret = Handshake.exponentWithModulo(Handshake.base, Handshake.secret, Handshake.prime)
                        }, Handshake.sharedSecret
                elseif initiatorData.type == "response" and Handshake.base > 0 and Handshake.secret > 0 then
                        Handshake.sharedSecret = Handshake.exponentWithModulo(initiatorData.moddedSecret, Handshake.secret, Handshake.prime)
                        return Handshake.sharedSecret
                else
                        return false
                end
        else
                return false
        end
end