Bank Server Software

	os.loadAPI("StrUtils")
	rednet.open("top")
	wire = peripheral.wrap("right")
	wire.open(1)
	
	num1=0 --Key Prime Number
	num2=0 --Key Power Number
	num3=0 --Key Secret Key
	num4=0 --Key Public Self
	num5=0 --Key Public Client
	key=0  --Encryption Key
	
	cpin=0 --Current User
	cid=0  --Current User
	
	function rednetWait(uid,mess)
			while true do
					local id,message = rednet.receive()
					if uid == id then
							if mess == message then
									break
							end
					end
			end
	end
	
	function isPrime(x)
			if x%3 == 0 then
					return false
			else
					local f = 5;
					while f <= math.floor(x^0.5) do
							if (x%f) == 0 then return false end
									if (x%(f+2)) == 0 then return false end
									f = f + 6;
							end
					end
			end
			return true
	end
	
	function agreeNums(id)
			num1=4
			while !isPrime(num1) do
					num1=math.random(0000,9999)
			end
			rednet.send(id,"p"..num1)
			rednetWait(id,"power")
			num2 = math.random(0000,9999)
			rednet.send(id,"m"..num2)
			rednetWait(id,"next")
	end
	
	function keyExchange(uid)
			agreeNums(uid)
			num3 = math.random(99999999999999999999999999)
			num4 = (num2 ^ num3) % num1
			rednet.send(uid,"l"..num4)
			while true do
					local id,message = rednet.receive()
					if uid == id then
							if message:sub(1,1) == "K" then
									break
							end
					end
			end
			num5=message:sub(2,-1)
			key=(num5 ^ num3) % num1
	end
	
	function recMes(mess,id)
			if mess == "keyx" then
					if cid == id then
							keyExchange(id)
					end
			end
			local mess = StrUtils.decrypt(mess,key)
			local messC = mess:sub(1,4)
			if cid == 0 then
					if messC == "logn" then
							wire.transmit(1,1,"L"..mess:sub(5,-1))
							local event, modemSide, senderChannel, replyChannel, message, senderDistance = os.pullEvent("modem_message")
							if message == "S" then
									cpin = mess:sub(5,8)
									cid = id
									rednet.send(id,StrUtils.encrypt("S",key))
							else
									rednet.send(id,StrUtils.encrypt("EBad Login",key))
							end
					end
			end
			if ccid == id then
					if messC == "newu" then
							local pin = math.random(1000,9999)
							rednet.send(id, StrUtils.encrypt("["..pin, key))
							wire.transmit(1,1,"+"..pin..mess:sub(5,-1))
							local event, modemSide, senderChannel, replyChannel, message, senderDistance = os.pullEvent("modem_message")
							if message == "S" then
									cpin = pin
									rednet.send(id,"S")
							else
									rednet.send(id,"E")
							end
					elseif messC == "sync" then
							local hash = StrUtils.SHA1(cpin..cid..key)
							if mess:sub(5,-1) == hash then
									rednet.send(id,StrUtils.encrypt("S",key))
							else
									rednet.send(id,StrUtils.encrypt("EError in Authenticating",key))
									cpin=0
									cid=0
									key=0
							end
					elseif messC == "tran" then
							wire.transmit(1,1,"T"..mess:sub(5,-1)
							rednet.send(id,StrUtils.encrypt("S",key))
					elseif messC == "bala" then
							wire.transmit(1,1,"B"..cpin)
							local event, modemSide, senderChannel, replyChannel, message, senderDistance = os.pullEvent("modem_message")
							rednet.send(id,StrUtils.encrypt("B"..message,key))
					elseif messC == "logo" then
							cpin=0
							cid=0
							key=0
					end
			end
	end
	
	function main()
			while true do
					id,message = rednet.receive()
					recMess(message,id)
			end
	end