DFSSDistributed Fair Signature System

DFSS is a simple and secure way to e-sign contracts with a large number of participants, ensuring fairness and minimizing the involvement of the trusted third party (TTP).

The DFSS project is developed by fourth year students of the Computer Science department of INSA Rennes.

The DFSS project is entirely Open-Source (MIT license)


Multi-party contract signing

Multi-party contracts involve at least two parties. Classical signing of a contract between more than two parties can be troublesome: all signers need to be physically present at the same place, and at the same time.

Electronic signature

Electronic signature is a way to legally sign a document using network communications and electronic credentials. It enables a signer to sign a contract from anywhere around the globe, without having to be physically present, nor to use the post mail services to deliver the signed documents.


DFSS implements an optimistic signing protocol, i.e. the DFSS users communicate directly with each other (P2P), without the TTP being a compulsory intermediary.


The signing protocol relies on combinatorial mathematics, and ensures fairness, i.e., either all signers get a signed contract, or no one gets a valid signature.


The DFSS application uses secure communications via TLS and software-related x509 certificates.


The DFSS application is available for the following operating systems:

  • Linux (32-bits, 64-bits, ARM)
  • Windows XP and the following (32-bits, 64-bits)
  • MacOS (32-bits, 64-bits)


DFSS application is composed of three entities:

  • The Platform handles the storage of contracts and the registration of users.

  • To sign a contract, users communicate with each other using DFSS Clients.

  • A client can contact the TTP if the signing protocol fails.


The DFSS project started in September 2015 and is currently developed by the following group of students from INSA Rennes:
Loïck Bonniot, Axel Caro, Tristan Claverie, Quentin Dauchy, Quentin Dufour, Yann Porret, and Maximilien Richer.

The project is supervised by Barbara Kordy and Gildas Avoine.

If you would like to contribute to the DFSS project, you will find all the necessary information on the following page.