Add Zeroize crate to project behind a default feature flag

Closes https://github.com/c0dearm/sharks/issues/8

Cargo.toml

@@ -17,14 +17,16 @@ codecov = { repository = "c0dearm/sharks" }
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 [features]
-default = ["std"]
+default = ["std", "zeroize_memory"]
 std = ["rand/std", "rand/std_rng"]
 fuzzing = ["std", "arbitrary"]
+zeroize_memory = ["zeroize"]
 
 [dependencies]
 rand = { version = "0.8", default-features = false }
 hashbrown = "0.9"
 arbitrary = { version = "0.4.7", features = ["derive"], optional = true }
+zeroize = { version = "1.2.0", features = ["zeroize_derive"], optional = true }
 
 [dev-dependencies]
 criterion = "0.3"

src/field.rs

@@ -7,6 +7,9 @@ use core::ops::{Add, Div, Mul, Sub};
 #[cfg(feature = "fuzzing")]
 use arbitrary::Arbitrary;
 
+#[cfg(feature = "zeroize_memory")]
+use zeroize::Zeroize;
+
 const LOG_TABLE: [u8; 256] = [
     0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
     0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81, 0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
@@ -63,6 +66,7 @@ const EXP_TABLE: [u8; 512] = [
 
 #[derive(Debug, PartialEq, Copy, Clone)]
 #[cfg_attr(feature = "fuzzing", derive(Arbitrary))]
+#[cfg_attr(feature = "zeroize_memory", derive(Zeroize))]
 pub struct GF256(pub u8);
 
 #[allow(clippy::suspicious_arithmetic_impl)]

src/share.rs

@@ -5,6 +5,9 @@ use super::field::GF256;
 #[cfg(feature = "fuzzing")]
 use arbitrary::Arbitrary;
 
+#[cfg(feature = "zeroize_memory")]
+use zeroize::Zeroize;
+
 /// A share used to reconstruct the secret. Can be serialized to and from a byte array.
 ///
 /// Usage example:
@@ -31,6 +34,7 @@ use arbitrary::Arbitrary;
 /// let secret = sharks.recover(&shares).unwrap();
 #[derive(Clone)]
 #[cfg_attr(feature = "fuzzing", derive(Arbitrary, Debug))]
+#[cfg_attr(feature = "zeroize_memory", derive(Zeroize))]
 pub struct Share {
     pub x: GF256,
     pub y: Vec<GF256>,