an open-source network simulator/emulator hybrid

runs real applications like Tor and Bitcoin over a simulated Internet topology

light-weight, efficient, scalable, parallelized, controllable, deterministic, accurate, modular, and more!

Easy installation

Be up and running in minutes with comprehensive and up-to-date setup guides.

Shadow Setup Instructions

Shadow Runs Tor!

A Shadow plug-in is available for quickly simulating Tor network topologies using the latest Tor software releases,

Tor Plug-in Instructions

Shadow Runs Bitcoin!

A Shadow plug-in is available for running Bitcoin nodes using the latest Bitcoin software releases.

Bitcoin Plug-in Instructions

Scalable and Efficient Design

Shadow was designed to be scalable, using multiple threads and processes during execution to parallelize simulation workloads. Shadow minimizes memory overhead, and is more efficient than emulation or other container approaches to experimentation.

View Design Overview

Simple for Beginners

Shadow contains everything you need to get started running simulations immediately.

Read Tutorials

Extensible for Experts

Shadow's modular design and plug-in architecture make it easy to customize simulations and run new applications. Shadow's default traffic generator can model complex user behaviors using the powerful dependency graph model and the standard GraphML XML syntax.

Browse Specifications

Grounded in Research

Shadow was originally designed as part of the following publication:

Rob Jansen and Nicholas Hopper. "Shadow: Running Tor in a Box for Accurate and Efficient Experimentation," Proceedings of the 19th Symposium on Network and Distributed System Security (NDSS), 2012.

  title = {Shadow: Running Tor in a Box for Accurate and Efficient Experimentation},
  author = {Rob Jansen and Nicholas Hopper},
  booktitle = {Proceedings of the 19th Symposium on Network and Distributed System Security (NDSS)},
  year = {2012},
  month = {February},
  publisher = {Internet Society},

Utilized in Practice

Shadow is used by groups at these fine establishments:

Get Informed

Original Shadow paper published at NDSS 2012
Design Overview
Modeling the Tor Network
Referencing Publications
Maintained by robgjansen

Get Involved

Contribute code
Report bugs: Shadow
Report bugs: Tor plug-in
Report bugs: Bitcoin plug-in