Crate clacc

This is a Rust implementanion of a CL universal accumulator as described in Efficient oblivious transfer with membership verification.

An accumulation is a fixed size digest that, along with the witness of an element’s addition, can be used to prove an element is a member of a set. The drawback to this solution is that any state changes to the accumulation invalidate the witneses of the other elements in the set, requiring computational resources to update them.

The benefit of CL accumulators is that they support efficient untrusted witness updates. The resource intensive task of updating witnesses can be outsourced to an untrusted party without sacrificing the integrity of the accumulator.

This project is focused on a use case where a central authority is both memory- and processing-constrained. The authority controls the private key and is able to add and delete elements while untrusted workers are able to recalculate witnesses provided they have access to the previous witnesses, the current state of the accumulator, and its public key.

Backends

This crate is built with a modular integer type backend. Integer types must implement the BigInt trait.

Optional Features

• bigint (default): Enable this feature to support ::num_bigint::BigInt as an integer type. ::num_bigint is a pure Rust big integer library.
• gmp: Enable this feature to support ::gmp::mpz::Mpz as an integer type. ::gmp is not a pure Rust library, but it is currently more performant than ::num_bigint.

Modules

• bigint
  Module for implementations using ::num_bigint.
• gmp
  Module for implementations using ::gmp.

Structs

• Accumulator
  An accumulator.
• ElementNotFoundError
• MissingPrivateKeyError
• Update
  A sum of updates to be applied to witnesses.

Traits

• BigInt
  A trait describing an arbitrary precision integer.