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Adding a Protocol

In order to illustrate how to create a virtual machine for a new protocol, we have created one with blanks to be filled in. It is defined in the following files:

Machines/no-party.cpp
Contains the main function.
Protocols/NoShare.h
Contains the :c:type:`NoShare` class, which is supposed to hold one share. :c:type:`NoShare` takes the cleartext type as a template parameter.
Protocols/NoProtocol.h

Contains a number of classes representing instances of protocols:

:c:type:`NoInput`
Private input.
:c:type:`NoProtocol`
Multiplication protocol.
:c:type:`NoOutput`
Public output.
Protocols/NoLivePrep.h
Contains the :c:type:`NoLivePrep` class, representing a preprocessing instance.

The number of blanks can be overwhelming. We therefore recommend the following approach to get started. If the desired protocol resembles one that is already implemented, you can check its code for inspiration. The main function of <protocol>-party.x can be found in Machines/<protocol>-party.cpp, which in turns contains the name of the share class. For example replicated-ring-party.x is implemented in Machines/replicated-ring-party.cpp, which refers to :c:func:`Rep3Share2` in Protocols/Rep3Share2.h. There you will find that it uses :c:func:`Replicated` for multiplication, which is found in Protocols/Replicated.h.

  1. Fill in the :c:func:`constant` static member function of :c:type:`NoShare` as well as the :c:func:`exchange` member function of :c:type:`NoOutput`. Check out :c:func:`DirectSemiMC<T>::exchange_` in Protocols/SemiMC.hpp for a simple example. It opens an additive secret sharing by sending all shares to all other parties and then summing up the received. See :ref:`this reference <network-reference>` for documentation on the necessary infrastructure. Constant sharing and public output allows to execute the following program:

    print_ln('%s', sint(123).reveal())

    This allows to check the correct execution of further functionality.

  2. Fill in the operator functions in :c:type:`NoShare` and check them:

    print_ln('%s', (sint(2) + sint(3)).reveal())
print_ln('%s', (sint(2) - sint(3)).reveal())
print_ln('%s', (sint(2) * cint(3)).reveal())

    Many protocols use these basic operations, which makes it beneficial to check the correctness

  3. Fill in :c:type:`NoProtocol`. Alternatively, if the desired protocol is based on Beaver multiplication, you can specify the following in :c:type:`NoShare`:

    typedef Beaver<This> Protocol;

    Then add the desired triple generation to :c:func:`NoLivePrep::buffer_triples()`. In any case you should then be able to execute:

    print_ln('%s', (sint(2) * sint(3)).reveal())

  4. In order to execute many kinds of non-linear computation, random bits are needed. After filling in :c:func:`NoLivePrep::buffer_bits()`, you should be able to execute:

    print_ln('%s', (sint(2) < sint(3)).reveal()