Proof of work for Electrum protocol

This script adds proof of work to the Electrum protocol.

The idea is that the Electrum network can fight the spam in a similar manner as was proposed for email with hashcash.

Written by Luca Venturini, based on an idea of Guido Dassori, sprouted on Telegram Channel Bitcoin Italia.

The script is adapted from tcp-proxy.pl by Peteris Krumins

Strategy

Instead of changing Electrum client or Electrum server, we put a proxy between the client and the Internet, and between the Internet and the server. The proxy on the client side calculates the proof of work and embeds it in the JSON request. The proxy on the server side checks the POW field, strips it away and sends to the server the same request that the client originally sent.

Electrum

Electrum-hashcash

Required libraries

On Debian:

apt-get install libjson-perl libdigest-sha-perl libstring-random-perl \
                libio-socket-ip-perl

Install on server side

Install ElectrumX
Start ElectrumX on port 40001:

TCP_PORT=40001 COIN=Bitcoin DB_DIRECTORY=path/to/db DAEMON_URL='http://user:pass@127.0.0.1:8332/' ./electrumx_server

Start the proxy, listening on port 30001:

git clone https://github.com/lucayepa/electrum-hashcash
cd electrum-hashcash
./hashcash-proxy-server.pl --listen_port=30001 --target_host=127.0.0.1 --target_port=40001

Install on client side with only one server

Install Electrum
Start the proxy, listening on port 50001:

git clone https://github.com/lucayepa/electrum-hashcash
cd electrum-hashcash
./hashcash-proxy-client.pl --listen_port=50001 --target_host=my.personal.server --target_port=30001

Start Electrum, using only one server, localhost on port 50001:

electrum -1 --server localhost:50001:t

IPv6

The program listens on IPv6 by using the option --listen_ipv6 on command line, and sends the connection to an IPv6 address by using the option --target_ipv6 on command line.

Readme sources and links

Electrum

@startuml
title Electrum
node "Client" #wheat {
  left to right direction
  object RPC_client {
    Generates request
  }
}
cloud "Internet" #silver {
  object TCP {
    JSON
  }
}
node "Server" #wheat {
  object RPC_server {
    Receives request
  }
}
RPC_client --> TCP : request
TCP --> RPC_server : request
@enduml

Electrum-hashcash

@startuml
title Electrum-hashcash
node "Client" #wheat {
  left to right direction
  object RPC_client {
    Generates request
  }
  object proxy_client #coral {
    Adds POW
  }
}
cloud "Internet" #silver {
  object TCP {
    JSON
  }
}
node "Server" #wheat {
  object proxy_server #coral {
    Checks POW
  }
  object RPC_server {
    Receives request
  }
}
RPC_client --> proxy_client : request
proxy_client --> TCP : request with POW
TCP --> proxy_server : request with POW
proxy_server --> RPC_server : request
@enduml