private-accumulator-proof-delegation

Cryptographic accumulators with privately delegatable proof updates in Rust. Supports RSA, class-group, and bilinear constructions.

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Warning

This is an academic prototype, it has not received careful code review. Therefore, this implementation is NOT ready for production use.

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Documentation

Add private-accumulator-proof-delegation to your repository

[dependencies]
private-accumulator-proof-delegation = "0.1.0"

Example

use num_bigint::{BigUint, ToBigInt};
use private_accumulator_proof_delegation::rsa_group::RsaGroup;
use private_accumulator_proof_delegation::RsaAccumulator;

let mut acc = RsaAccumulator::<RsaGroup>::setup();

// Add elements to the accumulator
let element = BigUint::from(7u32);
let ep = acc.add(&element);
for i in 2u32..5 {
    acc.add(&BigUint::from(i));
}

// Prove and verify membership
let proof = acc
    .mem_proof_create(&ep)
    .expect("element was just added; proof must exist");
assert!(acc.mem_ver(&proof, &ep));

// Prove and verify non-membership
let non_element = BigUint::from(383u32);
let product = acc.calculate_product_unreduced().to_bigint().unwrap();
let non_proof = acc
    .non_mem_proof_create(&non_element, &product)
    .expect("non-element is coprime with the set product");
assert!(acc.non_mem_ver(&non_proof, &non_element));

A runnable version lives in examples/basic_rsa.rs:

cargo run --example basic_rsa --release

Running the tests

cargo test

The default features (rsa, bilinear) require no system dependencies. The optional class-group feature pulls in class_group/curv-kzen and requires GMP and PARI to be installed (brew install gmp pari on macOS, apt-get install libgmp-dev pari-gp on Debian/Ubuntu):

cargo test --features class-group

Features

• RSA accumulator — membership and non-membership proofs in groups of unknown order.
• Class-group instantiation — a trapdoorless alternative to RSA: no trusted setup, at the cost of larger group elements and slower operations.
• Bilinear accumulator — KZG-style construction over BLS12-381.
• Privacy-preserving update delegation — clients blind their proofs before sending them to an untrusted server, the server updates the blinded proof, and the client verifies the work via NIZK proofs of discrete-log equality and unblinds to recover a valid up-to-date proof. The server learns nothing about the underlying element.
• Cargo features to opt into individual constructions: rsa and bilinear are on by default; enable class-group for the trapdoorless variant.

Benchmarks

cargo bench

Plotting helpers in figures/ reproduce the benchmark figures from the accompanying paper. They require Python with pandas, matplotlib, and seaborn installed.

Acknowledgements

This library builds on the work of the arkworks ecosystem (ark-ec, ark-ff, ark-poly-commit, ark-bls12-381), the class_group and curv-kzen crates for class-group arithmetic, and glass_pumpkin for safe-prime generation.