lox-extensions 0.1.0

A reputation-based bridge distribution system that provides privacy protection to users and their social graph while remaining open to all users.
Documentation 
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// The various credentials used by the system.

use cmz::*;
use curve25519_dalek::ristretto::RistrettoPoint as G;
use group::{ff, Group};
use rand::RngCore;

// A migration credential.
//
// This credential authorizes the holder of the Lox credential with the
// given id to switch from bucket from_bucket to bucket to_bucket. The
// migration_type attribute is 0 for trust upgrade migrations (moving
// from a 1-bridge untrusted bucket to a 3-bridge trusted bucket) and 1
// for blockage migrations (moving buckets because the from_bucket has
// been blocked).
// Annotated to "M"
CMZ! { Migration:
    lox_id,
    from_bucket,
    to_bucket,
    migration_type
}

// The main user credential in the Lox system.
//
// Its id is jointly generated by the user and the BA (bridge
// authority), but known only to the user. The level_since date is the
// Julian date of when this user was changed to the current trust
// level.
// Annotated to "L"
CMZ! { Lox:
    id,
    bucket,
    trust_level,
    level_since,
    invites_remaining,
    blockages
}

// The migration key credential.
//
// This credential is never actually instantiated. It is an implicit
// credential on attributes lox_id and from_bucket. This credential
// type does have an associated private and public key, however. The
// idea is that if a user proves (in zero knowledge) that their Lox
// credential entitles them to migrate from one bucket to another, the
// BA will issue a (blinded, so the BA will not know the values of the
// attributes or of Q) MAC on this implicit credential. The Q value
// will then be used (actually, a hash of lox_id, from_bucket, and Q)
// to encrypt the to_bucket, P, and Q fields of a Migration credential.
// That way, people entitled to migrate buckets can receive a Migration
// credential with their new bucket, without the BA learning either
// their old or new buckets.
// Annotated to "K"
CMZ! { MigrationKey:
    lox_id,
    from_bucket
}

// The Bucket Reachability credential.
//
// Each day, a credential of this type is put in each bucket that has
// at least a (configurable) threshold number of bridges that have not
// been blocked as of the given date. Users can present this
// credential (in zero knowledge) with today's date to prove that the
// bridges in their bucket have not been blocked, in order to gain a
// trust level.
// Annotated to "B"
CMZ! { BucketReachability:
    date,
    bucket
}

// The Invitation credential.
//
// These credentials allow a Lox user (the inviter) of sufficient trust
// (level 2 or higher) to invite someone else (the invitee) to join the
// system. The invitee ends up at trust level 1, in the _same bucket_
// as the inviter, and inherits the inviter's blockages count (so that
// you can't clear your blockages count simply by inviting yourself).
// Invitations expire after some amount of time.
// Annotated to "I"
CMZ! { Invitation:
    inv_id,
    date,
    bucket,
    blockages
}