Atom

Atom is an anonymous broadcasting system that allows users to send short messages while preserving their anonymity. This is particularly useful for things like anonymous whistleblowing and protest organization, where the sender may fear retaliation from powerful adversaries for sending certain messages. Atom is the first anonymous communication system that scales horiztonally while protecting against traffic analysis by global adversaries. Our SOSP'17 paper explains the system in detail.

The code posted here is a research prototype. While the code performs all the necessary crypto operations and should be fairly accurate in terms of performance, it is likely full of security bugs and security-criticial TODOs that hasn't been addressed. Pleae be careful if any part of this code is reused for other projects.

Requirements

The code requires Go 1.7 or later. The scripts are written in python. Most of the crypto operation relies on the DeDiS kyber library.

Components

• crypto: This implements all crypto operations used by Atom. There is a level of indirection from here to the kyber library, so that we can easily replace the crypto section of Atom without impacting rest of the code base.

• server: This implements both a physical server, and a logical server (member) which can be part of many groups. This part of the code actually carries out the protocol.

• client: Client program handles sending of the messages. Currently, each client program is responsible for sending many messages. From user's perspective, only Submit function should be relavant.

• directory: This is a very simple directory that keeps track of all participants and their keys.

• trustee: Trustees are only used in one variant of our protocol, and they serve as the final line of protection for users.

• db: This is a very simple database that stores all messages published in a given round so that users can download them.

Running the code

The code currently builds on the experimental main branch of the Kyber library. There is a chance future updates may break the code base. If you catch this, please file an issue and let us know!

To create all the executable, run

$ go install -tags experimental ./...

in the root folder.

There is an integration test availble in atom_test.go. This serves as both an example of the overall flow, and a test function. You can run this simply by doing

$ go test -v -tags experimental

in the root atom folder.

We also provide a way, run.py, to start individual processes, both local and remote, to test the code, rather than using the go test which just uses go routines. To run this, you first have to generate enough keys by running something like

$ mkdir $GOPATH/src/github.com/kwonalbert/atom/keys
$ $GOPATH/bin/keygen -numServers 1024 -numTrustees 32 -serverKeys $GOPATH/src/github.com/kwonalbert/atom/keys/server_keys.json -trusteeKeys $GOPATH/src/github.com/kwonalbert/atom/keys/trustee_keys.json

The same keys can be used for all experiments afterwards. Once the keys are set up, you are ready to run run.py. Running

$ run.py --help

will give you all available options. For example, the following command

$ /run.py --port 8000 --servers 8 --gsize 4 --groups 4 --clients 4 --trustees 4 --msgs 16 --msize 160 --type 1 --mode 1

runs a local Atom experiment with

• 16 servers
• 4 groups
• 4 trustees
• 16 messages per group
• 160 byte messages
• square network
• trap based protection.

Known problems and limitations

The current implementation just runs one round. There is some work that needs to be done to extend this code to do multiple rounds of communication.

This code was very recently migrated to the kyber library (from the old DeDiS library), and I've caught some weird bugs that arose as a result. I tried to squash as many as I could, but I think there are some more. If you run into them, please let me know. The current code uses ed25519 instead of nist-p256, since that portion of the code is not compiled by default in the new kyber library.

The script provided is very simple, and does not do fancy things for AWS; currently you need to have a separate script to set up your AWS network, and give in the instance description (from aws ec2 describe-instances) to the script to run it on AWS.

Contacts

If you have any problems with the code or want to learn more about it, don't hesitate to contact me at kwonal at mit.edu, or file an issue here.