Support no_std (#13)

* feat: support no_std

* simplify rng usage, update tests, upgrade version to 0.4

* fix workflow no-std test

* unignore doc-tests

* refactor tests

Co-authored-by: Aitor Ruano <codearm@pm.me>

.github/workflows/rust.yml

@@ -17,7 +17,7 @@ jobs:
         with:
           command: check
 
-  test:
+  test-std:
     name: Test
     runs-on: ubuntu-latest
     steps:
@@ -31,6 +31,21 @@ jobs:
         with:
           command: test
 
+  test-nostd:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --no-default-features
+
   format:
     name: Format
     runs-on: ubuntu-latest

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.4.0] - 2020-04-02
+### Added
+- It is now possible to compile without `std` with `--no-default-features`
+
 ## [0.3.3] - 2020-03-23
 ### Changed
 - Fix codecov badge

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sharks"
-version = "0.3.3"
+version = "0.4.0"
 authors = ["Aitor Ruano <codearm@pm.me>"]
 description = "Fast, small and secure Shamir's Secret Sharing library crate"
 homepage = "https://github.com/c0dearm/sharks"
@@ -16,12 +16,17 @@ maintenance = { status = "actively-developed" }
 codecov = { repository = "c0dearm/sharks" }
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+default = ["std"]
+std = ["rand/std"]
 
 [dependencies]
-rand = "0.7"
+rand = { version = "0.7", default-features = false }
+hashbrown = "0.7"
 
 [dev-dependencies]
 criterion = "0.3"
+rand_chacha = "0.2"
 
 [[bench]]
 name = "benchmarks"

README.md

@@ -17,7 +17,14 @@ Add this to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-sharks = "0.3"
+sharks = "0.4"
+```
+
+If your environment doesn't support `std`:
+
+```toml
+[dependencies]
+sharks = { version = "0.4", default-features = false }
 ```
 
 To get started using Sharks, see the [Rust docs](https://docs.rs/sharks)

src/field.rs

@@ -1,8 +1,8 @@
 // Basic operations overrided for the Galois Field 256 (2**8)
 // Uses pre-calculated tables for 0x11d primitive polynomial (x**8 + x**4 + x**3 + x**2 + 1)
 
-use std::iter::{Product, Sum};
-use std::ops::{Add, Div, Mul, Sub};
+use core::iter::{Product, Sum};
+use core::ops::{Add, Div, Mul, Sub};
 
 const LOG_TABLE: [u8; 256] = [
     0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
@@ -126,6 +126,7 @@ impl Product for GF256 {
 #[cfg(test)]
 mod tests {
     use super::{EXP_TABLE, GF256, LOG_TABLE};
+    use alloc::vec;
 
     #[test]
     fn add_works() {

src/lib.rs

@@ -1,25 +1,49 @@
 //! Fast, small and secure [Shamir's Secret Sharing](https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing) library crate
 //!
-//! Usage example:
+//! Usage example (std):
 //! ```
 //! use sharks::{ Sharks, Share };
 //!
 //! // Set a minimum threshold of 10 shares
 //! let sharks = Sharks(10);
 //! // Obtain an iterator over the shares for secret [1, 2, 3, 4]
+//! # #[cfg(feature = "std")]
+//! # {
 //! let dealer = sharks.dealer(&[1, 2, 3, 4]);
 //! // Get 10 shares
 //! let shares: Vec<Share> = dealer.take(10).collect();
 //! // Recover the original secret!
 //! let secret = sharks.recover(shares.as_slice()).unwrap();
 //! assert_eq!(secret, vec![1, 2, 3, 4]);
+//! # }
 //! ```
+//!
+//! Usage example (no std):
+//! ```
+//! use sharks::{ Sharks, Share };
+//! use rand_chacha::rand_core::SeedableRng;
+//!
+//! // Set a minimum threshold of 10 shares
+//! let sharks = Sharks(10);
+//! // Obtain an iterator over the shares for secret [1, 2, 3, 4]
+//! let mut rng = rand_chacha::ChaCha8Rng::from_seed([0x90; 32]);
+//! let dealer = sharks.dealer_rng(&[1, 2, 3, 4], &mut rng);
+//! // Get 10 shares
+//! let shares: Vec<Share> = dealer.take(10).collect();
+//! // Recover the original secret!
+//! let secret = sharks.recover(shares.as_slice()).unwrap();
+//! assert_eq!(secret, vec![1, 2, 3, 4]);
+//! ```
+#![no_std]
 
 mod field;
 mod math;
 mod share;
 
-use std::collections::HashSet;
+extern crate alloc;
+
+use alloc::vec::Vec;
+use hashbrown::HashSet;
 
 use field::GF256;
 pub use share::Share;
@@ -33,16 +57,50 @@ pub use share::Share;
 /// // Set a minimum threshold of 10 shares
 /// let sharks = Sharks(10);
 /// // Obtain an iterator over the shares for secret [1, 2, 3, 4]
+/// # #[cfg(feature = "std")]
+/// # {
 /// let dealer = sharks.dealer(&[1, 2, 3, 4]);
 /// // Get 10 shares
 /// let shares: Vec<Share> = dealer.take(10).collect();
 /// // Recover the original secret!
 /// let secret = sharks.recover(shares.as_slice()).unwrap();
 /// assert_eq!(secret, vec![1, 2, 3, 4]);
+/// # }
 /// ```
 pub struct Sharks(pub u8);
 
 impl Sharks {
+    /// This method is useful when `std` is not available. For typical usage
+    /// see the `dealer` method.
+    ///
+    /// Given a `secret` byte slice, returns an `Iterator` along new shares.
+    /// The maximum number of shares that can be generated is 256.
+    /// A random number generator has to be provided.
+    ///
+    /// Example:
+    /// ```
+    /// # use sharks::{ Sharks, Share };
+    /// # use rand_chacha::rand_core::SeedableRng;
+    /// # let sharks = Sharks(3);
+    /// // Obtain an iterator over the shares for secret [1, 2]
+    /// let mut rng = rand_chacha::ChaCha8Rng::from_seed([0x90; 32]);
+    /// let dealer = sharks.dealer_rng(&[1, 2], &mut rng);
+    /// // Get 3 shares
+    /// let shares: Vec<Share> = dealer.take(3).collect();
+    pub fn dealer_rng<R: rand::Rng>(
+        &self,
+        secret: &[u8],
+        rng: &mut R,
+    ) -> impl Iterator<Item = Share> {
+        let mut polys = Vec::with_capacity(secret.len());
+
+        for chunk in secret {
+            polys.push(math::random_polynomial(GF256(*chunk), self.0, rng))
+        }
+
+        math::get_evaluator(polys)
+    }
+
     /// Given a `secret` byte slice, returns an `Iterator` along new shares.
     /// The maximum number of shares that can be generated is 256.
     ///
@@ -54,14 +112,10 @@ impl Sharks {
     /// let dealer = sharks.dealer(&[1, 2]);
     /// // Get 3 shares
     /// let shares: Vec<Share> = dealer.take(3).collect();
+    #[cfg(feature = "std")]
     pub fn dealer(&self, secret: &[u8]) -> impl Iterator<Item = Share> {
-        let mut polys = Vec::with_capacity(secret.len());
-
-        for chunk in secret {
-            polys.push(math::random_polynomial(GF256(*chunk), self.0))
-        }
-
-        math::get_evaluator(polys)
+        let mut rng = rand::thread_rng();
+        self.dealer_rng(secret, &mut rng)
     }
 
     /// Given an iterable collection of shares, recovers the original secret.
@@ -71,8 +125,10 @@ impl Sharks {
     /// Example:
     /// ```
     /// # use sharks::{ Sharks, Share };
+    /// # use rand_chacha::rand_core::SeedableRng;
     /// # let sharks = Sharks(3);
-    /// # let mut shares: Vec<Share> = sharks.dealer(&[1]).take(3).collect();
+    /// # let mut rng = rand_chacha::ChaCha8Rng::from_seed([0x90; 32]);
+    /// # let mut shares: Vec<Share> = sharks.dealer_rng(&[1], &mut rng).take(3).collect();
     /// // Recover original secret from shares
     /// let mut secret = sharks.recover(&shares);
     /// // Secret correctly recovered
@@ -111,12 +167,27 @@ impl Sharks {
 #[cfg(test)]
 mod tests {
     use super::{Share, Sharks};
+    use alloc::{vec, vec::Vec};
+
+    impl Sharks {
+        #[cfg(not(feature = "std"))]
+        fn make_shares(&self, secret: &[u8]) -> impl Iterator<Item = Share> {
+            use rand_chacha::{rand_core::SeedableRng, ChaCha8Rng};
+
+            let mut rng = ChaCha8Rng::from_seed([0x90; 32]);
+            self.dealer_rng(secret, &mut rng)
+        }
+
+        #[cfg(feature = "std")]
+        fn make_shares(&self, secret: &[u8]) -> impl Iterator<Item = Share> {
+            self.dealer(secret)
+        }
+    }
 
     #[test]
     fn test_insufficient_shares_err() {
         let sharks = Sharks(255);
-        let dealer = sharks.dealer(&[1]);
-        let shares: Vec<Share> = dealer.take(254).collect();
+        let shares: Vec<Share> = sharks.make_shares(&[1]).take(254).collect();
         let secret = sharks.recover(&shares);
         assert!(secret.is_err());
     }
@@ -124,8 +195,7 @@ mod tests {
     #[test]
     fn test_duplicate_shares_err() {
         let sharks = Sharks(255);
-        let dealer = sharks.dealer(&[1]);
-        let mut shares: Vec<Share> = dealer.take(255).collect();
+        let mut shares: Vec<Share> = sharks.make_shares(&[1]).take(255).collect();
         shares[1] = Share {
             x: shares[0].x,
             y: shares[0].y.clone(),
@@ -137,8 +207,7 @@ mod tests {
     #[test]
     fn test_integration_works() {
         let sharks = Sharks(255);
-        let dealer = sharks.dealer(&[1, 2, 3, 4]);
-        let shares: Vec<Share> = dealer.take(255).collect();
+        let shares: Vec<Share> = sharks.make_shares(&[1, 2, 3, 4]).take(255).collect();
         let secret = sharks.recover(&shares).unwrap();
         assert_eq!(secret, vec![1, 2, 3, 4]);
     }

src/math.rs

@@ -1,5 +1,7 @@
 // A module which contains necessary algorithms to compute Shamir's shares and recover secrets
 
+use alloc::vec::Vec;
+
 use rand::distributions::{Distribution, Uniform};
 
 use super::field::GF256;
@@ -30,14 +32,13 @@ pub fn interpolate(shares: &[Share]) -> Vec<u8> {
 
 // Generates `k` polynomial coefficients, being the last one `s` and the others randomly generated between `[1, 255]`.
 // Coefficient degrees go from higher to lower in the returned vector order.
-pub fn random_polynomial(s: GF256, k: u8) -> Vec<GF256> {
+pub fn random_polynomial<R: rand::Rng>(s: GF256, k: u8, rng: &mut R) -> Vec<GF256> {
     let k = k as usize;
     let mut poly = Vec::with_capacity(k);
     let between = Uniform::new_inclusive(1, 255);
-    let mut rng = rand::thread_rng();
 
     for _ in 1..k {
-        poly.push(GF256(between.sample(&mut rng)));
+        poly.push(GF256(between.sample(rng)));
     }
     poly.push(s);
 
@@ -61,10 +62,13 @@ pub fn get_evaluator(polys: Vec<Vec<GF256>>) -> impl Iterator<Item = Share> {
 #[cfg(test)]
 mod tests {
     use super::{get_evaluator, interpolate, random_polynomial, Share, GF256};
+    use alloc::{vec, vec::Vec};
+    use rand_chacha::rand_core::SeedableRng;
 
     #[test]
     fn random_polynomial_works() {
-        let poly = random_polynomial(GF256(1), 3);
+        let mut rng = rand_chacha::ChaCha8Rng::from_seed([0x90; 32]);
+        let poly = random_polynomial(GF256(1), 3, &mut rng);
         assert_eq!(poly.len(), 3);
         assert_eq!(poly[2], GF256(1));
     }
@@ -81,7 +85,8 @@ mod tests {
 
     #[test]
     fn interpolate_works() {
-        let poly = random_polynomial(GF256(185), 10);
+        let mut rng = rand_chacha::ChaCha8Rng::from_seed([0x90; 32]);
+        let poly = random_polynomial(GF256(185), 10, &mut rng);
         let iter = get_evaluator(vec![poly]);
         let shares: Vec<Share> = iter.take(10).collect();
         let root = interpolate(&shares);

src/share.rs

@@ -1,3 +1,5 @@
+use alloc::vec::Vec;
+
 use super::field::GF256;
 
 /// A share used to reconstruct the secret. Can be serialized to and from a byte array.
@@ -5,12 +7,14 @@ use super::field::GF256;
 /// Usage example:
 /// ```
 /// use sharks::{Sharks, Share};
+/// # use rand_chacha::rand_core::SeedableRng;
 /// # fn send_to_printer(_: Vec<u8>) {}
 /// # fn ask_shares() -> Vec<Vec<u8>> {vec![vec![1, 2], vec![2, 3], vec![3, 4]]}
 ///
 /// // Transmit the share bytes to a printer
 /// let sharks = Sharks(3);
-/// let dealer = sharks.dealer(&[1, 2, 3]);
+/// let mut rng = rand_chacha::ChaCha8Rng::from_seed([0x90; 32]);
+/// let dealer = sharks.dealer_rng(&[1, 2, 3], &mut rng);
 ///
 /// // Get 5 shares and print paper keys
 /// for s in dealer.take(5) {
@@ -49,6 +53,7 @@ impl From<&[u8]> for Share {
 #[cfg(test)]
 mod tests {
     use super::{Share, GF256};
+    use alloc::{vec, vec::Vec};
 
     #[test]
     fn vec_from_share_works() {