qfall-schemes 0.1.1

Collection of prototype implementations of lattice-based cryptography
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// Copyright 2023 Phil Milewski
//
// This file is part of qFALL-schemes.
//
// qfall-schemes is free software: you can redistribute it and/or modify it under
// the terms of the Mozilla Public License Version 2.0 as published by the
// Mozilla Foundation. See <https://mozilla.org/en-US/MPL/2.0/>.

//! Contains traits and implementations related to Identity-Based Encryption (IBE) schemes.
//!
//! References:
//! - \[1\] Gentry, Craig and Peikert, Chris and Vaikuntanathan, Vinod (2008).
//!   Trapdoors for hard lattices and new cryptographic constructions.
//!   In: Proceedings of the fortieth annual ACM symposium on Theory of computing.
//!   <https://dl.acm.org/doi/pdf/10.1145/1374376.1374407>
//! - \[2\] Regev, Oded (2009).
//!   On lattices, learning with errors, random linear codes, and cryptography.
//!   In: Journal of the ACM 6.
//!   <https://dl.acm.org/doi/pdf/10.1145/1568318.1568324>

mod dual_regev_ibe;

pub use dual_regev_ibe::DualRegevIBE;
use qfall_math::integer::Z;

/// This trait should be implemented by every identity-based encryption scheme.
/// It offers a simple interface to use and implements the main functions supported by
/// IBEs.
pub trait IBEScheme {
    type MasterPublicKey;
    type MasterSecretKey;
    type SecretKey;
    type Cipher;
    type Identity;

    /// Generates a master public key pair `(mpk, msk)` suitable for the specific identity-based encryption scheme (IBE).
    ///
    /// Returns a tuple `(mpk, msk)` consisting of [`Self::MasterPublicKey`] and [`Self::MasterSecretKey`].
    fn setup(&self) -> (Self::MasterPublicKey, Self::MasterSecretKey);

    /// Extracts a secret key corresponding to the specified `identity` using the master secret key `msk`.
    ///
    /// Parameters:
    /// - `master_pk`: specifies the master public key
    /// - `master_sk`: specifies the master secret key used for extracting the secret of `identity`
    /// - `identity`: specifies the identity for which the secret key should be extracted
    ///
    /// Returns a secret key for the specified `identity` as a [`Self::SecretKey`].
    fn extract(
        &mut self,
        master_pk: &Self::MasterPublicKey,
        master_sk: &Self::MasterSecretKey,
        identity: &Self::Identity,
    ) -> Self::SecretKey;

    /// Encrypts the provided `message` using the master public key `mpk` and `identity` of the recipient.
    ///
    /// Parameters:
    /// - `master_pk`: specifies the master public key used for this IBE
    /// - `identity`: specifies the recipient that should be able to decrypt the encrypted message
    /// - `message`: specifies the message to be encrypted
    ///
    /// Returns the encryption of `message` as a [`Self::Cipher`] instance.
    fn enc(
        &self,
        master_pk: &Self::MasterPublicKey,
        identity: &Self::Identity,
        message: impl Into<Z>,
    ) -> Self::Cipher;

    /// Decrypts the provided `cipher` using the extracted secret key `sk`.
    ///
    /// Parameters:
    /// - `sk`: specifies the extracted secret key used for decryption
    /// - `cipher`: specifies the ciphertext to be decrypted
    ///
    /// Returns the decryption of `cipher` as a [`Z`] instance.
    fn dec(&self, sk: &Self::SecretKey, cipher: &Self::Cipher) -> Z;
}