blindsign

A rust library for computing and verifying blind signatures as part of the multi step blind signature scheme described in the paper Blind Signature Scheme Based on Elliptic Curve Cryptography.

About

Blind signatures allow for a requester to have a message signed without the signer knowing the content of the message. Additionally, although the signer and anyone with the signer's public key can authenticate the signature on the message, the signer cannot link the unblinded signature on the unblinded message to the blind signature on the blinded message.

The unlinkability of blind signatures to unblinded signatures, coupled with the ability to authenticate unblinded signatures on unblinded messages, makes blind signature schemes the go to algorithms for things such as anonymous E-cash, anonymous membership set constrained voting, and revocable anonymity.

Documentation

blindsign documentation gives detailed instructions on how to make use of the various components provided by this library.

Usage

Add this to your Cargo.toml:

[dependencies]
blindsign = "0.0.4"

And this to your crate root:

extern crate blindsign;

A complete sequence of using the protocol, with both client and server side steps represented linearly.

use sha3::Sha3_512;

use blindsign::{
    keypair::BlindKeypair,
    signature::{UnblindedSigData, WiredUnblindedSigData},
    request::BlindRequest,
    session::BlindSession,
    Error, Result,
};

// Generates a new keypair. The private key is used for creating blind
// signatures on the blinded message, and the public key is used for
// authenticating the unblinded signature on the unblinded message.
let keypair = BlindKeypair::generate().unwrap();

// Initiates a new blind session (bs) on the signer side, the first step of
// which is generating of the value R' (rp).
let (rp, bs) = BlindSession::new().unwrap();

// Initiates a new blind request on the requester side, which is input R' and
// generates e' (ep).
let (ep, br) = BlindRequest::new::<Sha3_512>(&rp).unwrap();

// Signs the e' value, which is essentially the blinded message hash. Produces
// S' (sp), which is the blind signature.
let sp = bs.sign_ep(&ep, keypair.private()).unwrap();

// Forms a new unblinded signed message object on the requester side, when
// provided with the blind signature previously generated by the signer
// side.
let unblinded_signed_msg = br.gen_signed_msg(&sp).unwrap();

// A demonstration of converting the unblinded signed message between
// internal representation and wired format for transmission over the
// network.
let wired = WiredUnblindedSigData::from(unblinded_signed_msg);
let sig = wired.to_internal_format().unwrap();

// A demonstration of authenticating the blind signature
assert!(sig.authenticate(keypair.public()));

License

• This implementation is licensed under MIT