Mandatory Hand-in 2: Virtual dice

The second mandatory hand-in in Security 1.

Purpose

In a peer-to-peer network, the assignment is to implement a coin-flipping protocol that allows Alice and Bob to roll a virtual dice over an insecure network (assumption: they do not trust each other). The commitment scheme is hash-based, and this ensures that the chosen statement is hidden from every node in the network, but at a later point, this statement can be revealed.

How to run

Open two terminals that represent Alice and Bob respectively. The format of the command-line input is

go run . <flag init> :<port> <port of other nodes> <name>

Here, the flag should only be set on one of the nodes, preferably Alice. This flag expects a boolean value afterwards which here should be true. If none are given, then the default value is false.

Expected command-line input

Alice’s terminal: go run . -init true :9000 9001 Alice
Bob’s terminal:   go run . :9001 9000 Bob

This exact input is given in the script run_split.ps1 which creates the two PowerShell terminal instances next to each other (shown below).

Errors

Since we are dealing with GRPC, Googles RPC framework, that connects services, sometimes errors occur.

RPC error

Error on server :: rpc error: code = Unavailable desc = connection error: desc = "transport: Error while dialing dial tcp [::1]:9001:

This happens when the Bob server takes too much time loading up. Close terminal, and try again.

Usage of more than one socket address

Server failed to listen af port :9001 :: listen tcp :9001: bind: Only one usage of each socket address (protocol/network address/port) is normally permitted.

If a previous terminal instance is not closed, then the error message of multiple socker address usage is shown. Close both terminals, and try again.