Add crate documentation

contract/tests/license_contract.rs

@@ -15,7 +15,7 @@ use execution_core::plonk::{Prover, Verifier};
 use rand::rngs::StdRng;
 use rand::{CryptoRng, RngCore, SeedableRng};
 use rkyv::{check_archived_root, Deserialize, Infallible};
-use zk_citadel::{circuit, gadgets, License, LicenseCreator, Request, SessionCookie};
+use zk_citadel::{circuit, gadgets, License, LicenseOrigin, Request, SessionCookie};
 
 const PROVER_BYTES: &[u8] = include_bytes!("../../target/prover");
 
@@ -56,7 +56,7 @@ fn create_test_license<R: RngCore + CryptoRng>(
     rng: &mut R,
 ) -> License {
     let request = Request::new(sk_user, pk_user, pk_lp, rng).unwrap();
-    License::new(attr, sk_lp, &LicenseCreator::FromRequest(request), rng).unwrap()
+    License::new(attr, sk_lp, &LicenseOrigin::FromRequest(request), rng).unwrap()
 }
 
 fn initialize() -> Session {
@@ -301,7 +301,7 @@ fn use_license_get_session() {
     let request =
         Request::new(&sk_user, &pk_user, &pk_lp, rng).expect("Request correctly created.");
     let attr = JubJubScalar::from(USER_ATTRIBUTES);
-    let license = License::new(&attr, &sk_lp, &LicenseCreator::FromRequest(request), rng).unwrap();
+    let license = License::new(&attr, &sk_lp, &LicenseOrigin::FromRequest(request), rng).unwrap();
 
     let license_blob = rkyv::to_bytes::<_, 4096>(&license)
         .expect("Request should serialize correctly")

core/CHANGELOG.md

@@ -10,7 +10,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Add `circuit` module
-- Add `LicenseCreator`
+- Add `LicenseOrigin`
+- Add crate documentation
 
 ### Changed
 

core/benches/license_circuit.rs

@@ -10,7 +10,7 @@ use dusk_poseidon::{Domain, Hash};
 use phoenix_core::{PublicKey, SecretKey};
 use poseidon_merkle::{Item, Tree};
 
-use zk_citadel::{circuit, gadgets, License, LicenseCreator, SessionCookie};
+use zk_citadel::{circuit, gadgets, License, LicenseOrigin, SessionCookie};
 
 use criterion::{criterion_group, criterion_main, Criterion};
 use rand_core::OsRng;
@@ -58,7 +58,7 @@ fn license_circuit_benchmark(crit: &mut Criterion) {
     let lic = License::new(
         &attr_data,
         &sk_lp,
-        &LicenseCreator::FromPublicKey(pk),
+        &LicenseOrigin::FromPublicKey(pk),
         &mut OsRng,
     )
     .expect("License correctly computed.");

core/src/circuit.rs

@@ -8,16 +8,23 @@ use crate::{gadgets, SessionCookie};
 use dusk_plonk::prelude::*;
 
 #[allow(dead_code)]
-pub const CAPACITY: usize = 15; // capacity required for the setup
-pub const DEPTH: usize = 16; // depth of the n-ary Merkle tree
 
+/// The capacity required for the setup
+pub const CAPACITY: usize = 15;
+/// The depth of the n-ary Merkle tree
+pub const DEPTH: usize = 16;
+
+/// A standard license circuit that simply uses the [`use_license`]
+/// gadget with no additional operations
 #[derive(Default, Debug)]
 pub struct LicenseCircuit {
     gp: gadgets::GadgetParameters<DEPTH>,
     sc: SessionCookie,
 }
 
 impl LicenseCircuit {
+    /// A method to create a new [`LicenseCircuit`] from some [`GadgetParameters`]
+    /// and a [`SessionCookie`]
     pub fn new(gp: &gadgets::GadgetParameters<DEPTH>, sc: &SessionCookie) -> Self {
         Self { gp: *gp, sc: *sc }
     }

core/src/error.rs

@@ -7,7 +7,6 @@
 use core::fmt;
 
 /// All possible errors for Citadel
-#[allow(missing_docs)]
 #[allow(clippy::enum_variant_names)]
 #[derive(Debug, Clone)]
 pub enum Error {

core/src/gadgets.rs

@@ -23,18 +23,18 @@ use crate::{license::LIC_PLAINTEXT_SIZE, License, SessionCookie};
 
 use poseidon_merkle::zk::opening_gadget;
 
-// out of this circuit, the generated public inputs vector collects
-// these values in that particular order:
-//
-// public_inputs[0]: session_id
-// public_inputs[1]: session_hash
-// public_inputs[2]: com_0
-// public_inputs[3]: com_1.x
-// public_inputs[4]: com_1.y
-// public_inputs[5]: com_2.x
-// public_inputs[6]: com_2.y
-// public_inputs[7]: root
-
+/// The [`use_license`] gadget for the [`LicenseCircuit`]. It is meant
+/// to use Citadel licenses on-chain. Out of this circuit, the generated
+/// public inputs vector collects these values in that particular order:
+///
+/// session_id
+/// session_hash
+/// com_0
+/// com_1.x
+/// com_1.y
+/// com_2.x
+/// com_2.y
+/// root
 pub fn use_license<const DEPTH: usize>(
     composer: &mut Composer,
     gp: &GadgetParameters<DEPTH>,
@@ -110,24 +110,25 @@ pub fn use_license<const DEPTH: usize>(
     Ok(())
 }
 
+/// The parameters required by the [`use_license`] gadget
 #[cfg_attr(
     feature = "rkyv-impl",
     derive(Archive, Serialize, Deserialize),
     archive_attr(derive(bytecheck::CheckBytes))
 )]
 #[derive(Debug, Clone, Copy)]
 pub struct GadgetParameters<const DEPTH: usize> {
-    pub lpk: JubJubAffine,   // license public key
-    pub lpk_p: JubJubAffine, // license public key prime
-    pub sig_lic: Signature,  // signature of the license
+    lpk: JubJubAffine,   // license public key
+    lpk_p: JubJubAffine, // license public key prime
+    sig_lic: Signature,  // signature of the license
 
-    pub com_0: BlsScalar,      // Hash commitment 0
-    pub com_1: JubJubExtended, // Pedersen Commitment 1
-    pub com_2: JubJubExtended, // Pedersen Commitment 2
+    com_0: BlsScalar,      // Hash commitment 0
+    com_1: JubJubExtended, // Pedersen Commitment 1
+    com_2: JubJubExtended, // Pedersen Commitment 2
 
-    pub session_hash: BlsScalar,           // hash of the session
-    pub sig_session_hash: SignatureDouble, // signature of the session_hash
-    pub merkle_proof: Opening<(), DEPTH>,  // Merkle proof for the Proof of Validity
+    session_hash: BlsScalar,           // hash of the session
+    sig_session_hash: SignatureDouble, // signature of the session_hash
+    merkle_proof: Opening<(), DEPTH>,  // Merkle proof for the Proof of Validity
 }
 
 impl<const DEPTH: usize> Default for GadgetParameters<DEPTH> {
@@ -156,6 +157,7 @@ impl<const DEPTH: usize> Default for GadgetParameters<DEPTH> {
 }
 
 impl<const DEPTH: usize> GadgetParameters<DEPTH> {
+    /// Method to generate the [`GadgetParameters`] struct
     #[allow(clippy::too_many_arguments)]
     pub fn compute_parameters<R: RngCore + CryptoRng>(
         sk: &SecretKey,

core/src/lib.rs

@@ -4,14 +4,31 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
+//! This package contains the core implementation of Citadel, a self-sovereign identity protocol for
+//! decentralized networks, allowing users to receive licenses issued by license providers (LP), and
+//! to use them to prove sensitive information in zero-knowledge to service providers (SP).
+//!
+//! Reference: https://arxiv.org/pdf/2301.09378
+//!
+//! **DISCLAIMER**: this package **has not gone through an exhaustive security analysis**,
+//! so it is not intended to be used in a production environment, only for academic purposes.
+
+#![deny(missing_docs)]
+
 mod error;
 mod license;
 mod request;
 mod session;
 
+/// The arithmetic circuit module to use licenses
 pub mod circuit;
+
+/// The gadget module required by the license circuit and / or
+/// in third party circuits, to use licenses
 pub mod gadgets;
 
-pub use license::{License, LicenseCreator};
+pub use license::{License, LicenseOrigin};
 pub use request::Request;
 pub use session::{Session, SessionCookie};
+
+pub use error::Error;

core/src/license.rs

@@ -8,7 +8,7 @@ use dusk_bytes::Serializable;
 use dusk_jubjub::dhke;
 use dusk_poseidon::{Domain, Hash};
 use ff::Field;
-use jubjub_schnorr::{SecretKey as NoteSecretKey, Signature};
+use jubjub_schnorr::{SecretKey as LicenseSecretKey, Signature};
 use phoenix_core::{
     aes::{decrypt, encrypt, ENCRYPTION_EXTRA_SIZE},
     Error, PublicKey, SecretKey, StealthAddress,
@@ -26,31 +26,39 @@ use crate::request::{Request, REQ_PLAINTEXT_SIZE};
 pub(crate) const LIC_PLAINTEXT_SIZE: usize = Signature::SIZE + JubJubScalar::SIZE;
 const LIC_ENCRYPTION_SIZE: usize = LIC_PLAINTEXT_SIZE + ENCRYPTION_EXTRA_SIZE;
 
-pub enum LicenseCreator {
+/// Enumeration used to create new licenses
+pub enum LicenseOrigin {
+    /// From a [`Request`] sent on-chain
     FromRequest(Request),
+    /// From a [`PublicKey`] of a given user
     FromPublicKey(PublicKey),
 }
 
+/// The struct defining a Citadel license, an asset that represents
+/// the right of a user to use a specific service
 #[cfg_attr(
     feature = "rkyv-impl",
     derive(Archive, Serialize, Deserialize),
     archive_attr(derive(bytecheck::CheckBytes))
 )]
 #[derive(Debug, Clone)]
 pub struct License {
-    pub lsa: StealthAddress,            // license stealth address
-    pub enc: [u8; LIC_ENCRYPTION_SIZE], // encryption of the license signature and attribute data
+    /// The stealth address of the license
+    pub lsa: StealthAddress,
+    /// The encryption of the license signature and the attribute data     
+    pub enc: [u8; LIC_ENCRYPTION_SIZE],
 }
 
 impl License {
+    /// Method to generate a new [`License`]
     pub fn new<R: RngCore + CryptoRng>(
         attr_data: &JubJubScalar,
         sk_lp: &SecretKey,
-        lc: &LicenseCreator,
+        lo: &LicenseOrigin,
         rng: &mut R,
     ) -> Result<Self, Error> {
-        let (lsa, k_lic) = match lc {
-            LicenseCreator::FromRequest(req) => {
+        let (lsa, k_lic) = match lo {
+            LicenseOrigin::FromRequest(req) => {
                 let k_dh = dhke(sk_lp.a(), req.rsa.R());
                 let dec: [u8; REQ_PLAINTEXT_SIZE] = decrypt(&k_dh, &req.enc)?;
 
@@ -66,7 +74,7 @@ impl License {
 
                 (lsa, k_lic)
             }
-            LicenseCreator::FromPublicKey(pk_user) => {
+            LicenseOrigin::FromPublicKey(pk_user) => {
                 let r_dh = JubJubScalar::random(&mut *rng);
                 let lsa = pk_user.gen_stealth_address(&r_dh);
                 let k_lic = dhke(&r_dh, pk_user.A());
@@ -81,7 +89,7 @@ impl License {
             Domain::Other,
             &[lpk.get_u(), lpk.get_v(), BlsScalar::from(*attr_data)],
         )[0];
-        let sig_lic = NoteSecretKey::from(sk_lp.a()).sign(rng, message);
+        let sig_lic = LicenseSecretKey::from(sk_lp.a()).sign(rng, message);
 
         let mut plaintext = sig_lic.to_bytes().to_vec();
         plaintext.append(&mut attr_data.to_bytes().to_vec());

core/src/request.rs

@@ -23,18 +23,24 @@ use dusk_plonk::prelude::*;
 pub(crate) const REQ_PLAINTEXT_SIZE: usize = StealthAddress::SIZE + JubJubAffine::SIZE;
 const REQ_ENCRYPTION_SIZE: usize = REQ_PLAINTEXT_SIZE + ENCRYPTION_EXTRA_SIZE;
 
+/// The struct defining a Citadel request, a set of information that
+/// a user sends to the network to inform a LP that the user is
+/// requesting a license from them
 #[cfg_attr(
     feature = "rkyv-impl",
     derive(Archive, Serialize, Deserialize),
     archive_attr(derive(bytecheck::CheckBytes))
 )]
 #[derive(Debug)]
 pub struct Request {
-    pub rsa: StealthAddress,            // request stealth address
-    pub enc: [u8; REQ_ENCRYPTION_SIZE], // encryption of the license stealth address and k_lic
+    /// The stealth address for the request
+    pub rsa: StealthAddress,
+    /// The encryption of the license stealth address and the k_lic symmetric key
+    pub enc: [u8; REQ_ENCRYPTION_SIZE],
 }
 
 impl Request {
+    /// Method to create a new [`Request`] given ther user keys and the public key of LP
     pub fn new<R: RngCore + CryptoRng>(
         sk_user: &SecretKey,
         pk_user: &PublicKey,

core/src/session.rs

@@ -14,22 +14,33 @@ use rkyv::{Archive, Deserialize, Serialize};
 
 use dusk_plonk::prelude::*;
 
+/// The struct defining a Citadel session, a set of public values shared
+/// on-chain that represent the use of a service by an unknown user
 #[cfg_attr(
     feature = "rkyv-impl",
     derive(Archive, Serialize, Deserialize),
     archive_attr(derive(bytecheck::CheckBytes))
 )]
 #[derive(Debug)]
 pub struct Session {
+    /// The hash of the public key of the SP and a nonce
     pub session_hash: BlsScalar,
+    /// The ID of the [`Session`], computed as the hash of
+    /// the lpk' and the challenge
     pub session_id: BlsScalar,
-
-    pub com_0: BlsScalar,      // Hash commitment 0
-    pub com_1: JubJubExtended, // Pedersen Commitment 1
-    pub com_2: JubJubExtended, // Pedersen Commitment 2
+    /// The hash commitment 0 from the license circuit,
+    /// that commits to the public key of the LP
+    pub com_0: BlsScalar,
+    /// The Pedersen commitment 1 from the license circuit,
+    /// that commits to the attribute data
+    pub com_1: JubJubExtended,
+    /// The Pedersen commitment 2 from the license circuit,
+    /// that commits to the challenge
+    pub com_2: JubJubExtended,
 }
 
 impl Session {
+    /// Method that generates a [`Session`] from a public inputs vector
     pub fn from(public_inputs: &[BlsScalar]) -> Self {
         let session_id = public_inputs[0];
         let session_hash = public_inputs[1];
@@ -54,6 +65,8 @@ impl Session {
         }
     }
 
+    /// Method that verifies a [`SessionCookie`], by checking if all the
+    /// openings match the commitments of the given [`Session`]
     pub fn verify(&self, sc: SessionCookie) -> Result<(), Error> {
         let session_hash =
             Hash::digest(Domain::Other, &[sc.pk_sp.get_u(), sc.pk_sp.get_v(), sc.r])[0];
@@ -80,22 +93,34 @@ impl Session {
     }
 }
 
+/// The struct defining a session cookie, a secret value
+/// known only by the user and the SP, used to verify that
+/// a given session is correct
 #[cfg_attr(
     feature = "rkyv-impl",
     derive(Archive, Serialize, Deserialize),
     archive_attr(derive(bytecheck::CheckBytes))
 )]
 #[derive(Default, Debug, Clone, Copy)]
 pub struct SessionCookie {
-    pub pk_sp: JubJubAffine, // public key of the SP
-    pub r: BlsScalar,        // randomness for session_hash
+    /// Public key of the SP
+    pub pk_sp: JubJubAffine,
+    /// Randomness for session_hash
+    pub r: BlsScalar,
+    /// The ID of the session
     pub session_id: BlsScalar,
 
-    pub pk_lp: JubJubAffine,     // public key of the LP
-    pub attr_data: JubJubScalar, // attribute data of the license
-    pub c: JubJubScalar,         // challenge value
-
-    pub s_0: BlsScalar,    // randomness for com_0
-    pub s_1: JubJubScalar, // randomness for com_1
-    pub s_2: JubJubScalar, // randomness for com_2
+    /// Public key of the LP
+    pub pk_lp: JubJubAffine,
+    /// Attribute data of the license
+    pub attr_data: JubJubScalar,
+    /// Challenge value
+    pub c: JubJubScalar,
+
+    /// Randomness for com_0
+    pub s_0: BlsScalar,
+    /// Randomness for com_1
+    pub s_1: JubJubScalar,
+    /// Randomness for com_2
+    pub s_2: JubJubScalar,
 }