An MPC playground in Scala

Welcome! In this repository you will find a basic embedding of secure multi-party computations in Scala.

MPC

MPC is a subfield in cryptography with the goal of creating methods for parties to jointly compute a function over their inputs while keeping those inputs private. In the MPC.scala file we provide an abstract implementation of such a setting. Of particular interest:

• We define abstract types PublicNum from SecretNum which distinguish the format of plaintext values from secret shared ones. Both these formats allow for addition and multiplication via their respective implicit typeclasses.
• The SharedNum type represents secret shares of a number that are distributed amongst multiple players. We use an Array to represent the various players. In reality the value of each index would reside at the site of a given player.
• We define conversions from PublicNum to SharedNum, and vice-versa. The act of converting a SharedNum to a PublicNum is known as reveal.
• Our model of computation has a trusted dealer, represented here by a global random generator. Its job is to create secret shares for given numbers (createShares).
• We then define addition and multiplication on SharedNum.

An implementation of the MPC interface can be found in [LongMPC.scala]](https://github.com/Inpher/scala-mpc-playground/blob/master/src/main/scala/mpc/LongMPC.scala), where we set the format of both public and secret values to Long. A basic test of multiplication can be found in the LongMPCImpl object.

DSL

We define a very simple DSL that allows trivial manipulations of Vectors (DSL.scala). In this DSL, we have two abstract types, Long (different from the actual scala.Long) and Vector. Exercise: can you add Matrices? We can implement this interface two ways:

• The classic implementation, i.e. plaintext only. Here, both abstract types take traditional values (the DSL Long becomes scala.Long, and the DSL Vector becomes a simple scala.Array).
• The MPC implementation.

Finally, a basic test shows how to run a program in different contexts.